UNIVERSTTYsfttUFORNIA 


COLLEGE  of  MINING 

DEPARTMENTAL 
LIBRARY 


BEQUEST  OF 


SAMUELBENEDICTCHRISTY 

PROFESSOR  OF 

MINING  AND   METALLURGY 

1885-1914 


TEXT-BOOK 


OF 


GEOLOGY 


DESIGNED 


FOE,  SCHOOLS  AND  ACADEMIES. 


BY 

JAMES  D.  DANA,  LL.D., 

AUTHOR  OF  "A  MANUAL  OF  GEOLOGY,"  "A  SYSTEM  OF  MINERALOGY,"  OF  REPORTS 

OF  WILKES'S  EXPLORING  EXPEDITION  ON  GEOLOGY,  ZOOPHYTES,  AND 

CRUSTACEA,  "CORALS  AND  CORAL  ISLANDS,"  ETC. 


§E&ttton. 


ILLUSTRATED   BY   400   WOODCUTS. 


IVISON,  BLAKEMAN",  TAYLOR,  &  CO., 
NEW  YORK  AND  CHICAGO. 


Entered,  according  to  Act  of  Congress,  in  the  year  1863, 
BY    THEODORE    BLISS    &    CO., 

in  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the  Eastern 
District  of  Pennsylvania. 


Entered  according  to  Act  of  Congress,  in  the  year  1874, 

BY    IVISON,    BLAKEMAN,    TAYLOR,    &    CO., 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


UNIVERSITY  PRESS  :  WELCH,  BIGELOW,  &  Co., 
CAMBRIDGE. 


PREFACE. 


IN  preparing  this  abridgment  of  my  Manual  of  Geology, 
the  arrangement  of  the  larger  work  has  been  retained.  The 
science  is  not  made  a  dry  account  of  rocks  and  their  fossils, 
but  a  history  of  the  earth's  continents,  seas,  strata,  moun- 
tains, climates,  and  living  races;  and  this  history  is  illus- 
trated, as  far  as  the  case  admits,  by  means  of  American  facts, 
without,  however,  overlooking  those  of  other  continents,  and 
especially  of  Great  Britain  and  Europe. 

No  glossary  of  scientific  terms  has  been  inserted,  because 
the  volume  is  throughout  a  glossary,  or  a  book  of  explana- 
tions of  such  terms,  and  it  is  only  necessary  to  refer  to  the 
Index  to  find  where  the  explanations  are  given. 

The  teacher  of  Geology,  and  the  student  who  would  ex- 
tend his  inquiries  beyond  his  study  or  recitation-room,  is 
referred  to  the  Manual  for  fuller  explanations  of  all  points 
that  come  under  discussion  in  the  Text-book,  —  including 
a  more  complete  survey  of  the  rock-formations  of  America 
and  other  parts  of  the  world,  with  many  sections  and  details 
of  local  geology,  —  a  much  more  copious  exhibition  of  the 
ancient  life  of  the  several  epochs  and  periods  and  of  the 
principles  deduced  from  the  succession  of  living  species  on 

303417 


iv  PREFACE. 

the  globe,  —  a  more  thorough  elucidation  of  the  depart- 
ments of  Physiographic  and  Dynamical  Geology,  —  a  chap- 
ter on  the  Mosaic  Cosmogony,  —  a  large  number  of  addi- 
tional woodcut  illustrations,  with  references  to  authorities, 
and  personal  acknowledgments,  besides  a  general  chart  of 
the  world. 

This  second  edition  of  the  Text-book  has  been  changed 
throughout,  so  as  to  make  it  conform  in  all  respects  to  the 
new  edition  of  the  Manual. 

NEW  HAVEN,  CT.,  November  2,  1874. 


TABLE   OF   CONTENTS. 


PAGE 
INTRODUCTION  1 


PART  I.— Physiographic  Geology. 

1.  General  Characteristics  of  the  Earth's  Features    ....  5 

2.  System  in  the  Earth's  Features 8 

PART  II.  — Lithological  Geology. 

I.  CONSTITUTION  OF  ROCKS 14 

1.  General  Observations  on  their  Constituents        .         .         .  14 

2.  Kinds  of  Rocks 20 

II.  CONDITION,  STRUCTURE,  AND  ARRANGEMENT  OF  ROCK-MASSES  27 

Stratified  Condition  . 31 

1.  Structure 31 

2.  Positions  of  Strata 37 

3.  Order  of  Arrangement  of  Strata         ....  44 

REVIEW  OF  THE  ANIMAL  AND  VEGETABLE  KINGDOMS. 

1.  Animal  Kingdom        .........  48 

2.  Vegetable  Kingdom 60 

PART  III.  —  Historical  Geology. 

General  Observations      .         .  .         .         .         .         .         .         .64 

I.  ARCHAEAN  TIME 73 

II.  PALEOZOIC  TIME .        .78 

I.  AGE  OF  INVERTEBRATES,  OR  SILURIAN  AGE  ...  79 

1.  Primordial  Period 80 

2.  Canadian  and  Trenton  Periods  .        .        .         .        .  84 

3.  Upper  Silurian  Era 93 


vi  CONTENTS. 

II.  PALEOZOIC  TIME  (continued). 

II.  AGE  OF  FISHES,  OK  DEVONIAN  AGE        V      .-«•       .  .     103 

III.  CARBONIFEROUS  AGE,  OR  AGE  OF  COAL  PLANTS  .  .         114 

GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC         *        .  .     140 

DISTURBANCES  CLOSING  PALEOZOIC  TIME  ...  .         150 

III.  MESOZOIC  TIME  .        .-        .      ..  *        .        .        .        .  .     157 

REPTILIAN  AGE         .        .        .        .        .        .        ...  158 

1.  Triassic  and  Jurassic  Periods        .         .         .         .  .159 

2.  Cretaceous  Period    .         ...         .         .  -      -..-.  .-  -     184 

GENERAL  OBSERVATIONS  ON  THE  MESOZOIC  .        «•        .  .     196 

IV.  CENOZOIC  TIME       >. .::..         .        .      .;      ,.      i.  .         201 

I.  TERTIARY  AGE,  OR  AGE  OF  MAMMALS      .        .        .  .     202 

II.  QUATERNARY  AGE,  OR  ERA  OF  MAN    .       *     ,  ..  .         219 

1.  Glacial  Period     .        .         .        .         .        v        .  .     220 

2.  Champlain  Period    .        .         ...      ...,'...  .         225 

3.  Recent  Period     .     ';.'./."'.        .  .     229 
III.  LIFE  OF  THE  QUATERNARY  .        .              '!;        .''  .         232 

GENERAL  OBSERVATIONS  ON  CENOZOIC  TIME        .- :_  ;.  .    243 

V.  GENERAL  OBSERVATIONS  ON  GEOLOGICAL  HISTORY    245 


PART  IV.  —  Dynamical  Geology. 

I.  LIFE         .        ."....        .        .        .        .        .        .  264 

1.  Peat  Formations    .  .        .         ,         .        .         .  265 

2.  Beds  of  Microscopic  Organisms 267 

3.  Coral  Reefs .."      *        .         .         .  268 

II.  THE  ATMOSPHERE    .        .        »       .        .        .        .        .        .  273 

III.  WATER . .     I  .        .  275 

1.  Fresh  Waters     .        .        ,     <    .        .      .  .  ?     .        ,        .  275 

2.  The  Ocean      .        .        .        .        .  :      .        .        .        .  286 

3.  Freezing  and  Frozen  Waters,  Glaciers,  Icebergs  .         .         .  294 

IV.  HEAT 303 

1.  Expansion  and  Contraction 305 

2.  Igneous  Action  and  Results 306 

3.  Metamorphism 319 

4.  Formation  of  Veins  323 


CONTENTS.  vii 

V.  THE  EARTH  A  COOLING  GLOBE:  ITS  CONSEQUENCES  .        .     327 

1.  General  Considerations  ......  .         327 

2.  General  Results  of  the  Lateral  Pressure       .         .  .         .     329 

3.  Evolution  of  the  Earth's  Fundamental  Features      .  .         331 

4.  Formation  of  Mountain  Chains 334 

VI.  CONCLUDING  REMARKS  342 


APPENDIX. 

1.  Catalogue  of  American  Localities  of  Fossils      .         .         .  .         .346 

2.  Geological  Implements,  etc.          .         .         ....  ,         350 

INDEX  353 


INTRODUCTION. 


1.  Rock-structure  of  the  earth's  crust.  —  Beneath  the  soil 
and  waters  of  the  earth's  surface  there  is  everywhere  a  base- 
ment of  rocks.  The  rocky  bluffs  forming  the  sides  of  many 
valleys,  the  ledges  about  the  tops  of  hills  and  mountains, 
and  the  cliffs  along  sea-shores,  are  portions  of  this  basement 
exposed  to  view. 

The  rocks  generally  lie  in  beds ;  and  these  beds  vary  from 
a  few  inches  to  hundreds  of  yards  in  thickness.  The  differ- 
ent kinds  are  spread  out  one  over  another,  in  many  alterna- 
tions. Sometimes  they  are  in  horizontal  layers ;  but  very 
often  they  are  inclined,  as  if  they  had  been  pushed  out  of 
their  original  position.  In  some  regions  they  are  soft  and 
crumbling ;  in  others  they  are  not  only  hard,  but  also  crystal- 
line in  texture.  Moreover,  they  are  not  all  found  in  any  one 
country. 

By  careful  study  of  the  rocks  of  different  continents  it 
has  been  ascertained  that  the  series  of  beds,  if  all  were  in 
one  pile,  would  have  a  thickness  of  18  or  20  miles.  The 
actual  thickness  in  niost  regions  is  far  less  than  this. 

These  18  or  20  miles  out  of  the  4,000  miles  between  the 
earth's  surface  and  centre  are  all  of  the  great  sphere  that 
are  within  reach  of  observation. 

The  series  of  rocks  alluded  to  overlie,  beyond  all  question, 
crystalline  rocks  that  are  not  part  of  the  series.  There  is 
good  reason  for  believing,  also,  that,  not  many  scores  of 
miles  below  the  surface,  there  are  regions  of  melted  rocks  or 
fire  seas  of  great  extent.  These  fiery  depths  are  nowhere  open 


2  INTRODUCTION. 

to  examination ;  yet  the  rocks  ejected  in  a  melted  state  from 
volcanoes  or  from  the  earth's  fissures  are  supposed  to  afford 
indications  of  what  they  contain. 

2.  Facts  taught  by  the  arrangement  and  structure  of  the  rocks. 
—  The  various  rocks  afford  proof  that  they  were  all  slowly  or 
gradually  made,  —  the  lowest  in  the  series,  of  course,  first,  and 
so  on  upward  to  the  last.  The  lowest,  therefore,  belong  to  an 
early  period  of  the  world,  and  those  above  to  later  periods,  in 
succession. 

The  larger  part  of  them  bear  evidence  that  originally  they 
were  deposits  or  accumulations  of  sand,  mud,  or  pebbles  in  a 
shallow  ocean,  and  that  the  material  was  laid  down  or  arranged 
by  the  waves  and  currents  of  the  same  ocean,  just  as  beds  of 
sand,  mud,  or  gravel  are  now  made  off  sea-shores,  or  along 
sea-beaches ;  others  indicate  that  they  were  formed  by  the 
action  of  the  waters  of  lakes  or  of  rivers ;  and  others  still,  that 
the  sands  of  which  they  consist  were  gathered  together  by  the 
drifting  winds,  as  sands  are  drifted  and  heaped  up  near  vari- 
ous sea-coasts.  In  many  of  the  rocks  there  are  marks  on  the 
layers  that  were  made  by  the  rippling  waves,  or  by  the  cur- 
rents, when  the  material  of  the  bed  was  loose  sand  or  clay ; 
or  there  are  cracks  —  though  now  filled  —  that  were  opened 
by  the  drying  sun  in  an  exposed  mud-flat;  or  impressions 
that  were  produced  by  the  drops  of  a  fall  of  rain.  Thus  the 
beds  themselves  make  known  the  conditions  under  which 
they  were  formed,  and  thereby  the  depth  and  outline  of  the 
continental  seas. 

Again,  in  some  regions,  the  rocks,  after  being  consolidated, 
have  been  profoundly  fractured,  and  the  fissures  thus  opened 
have  been  filled  with  melted  rock  proceeding  from  the  depths 
below. 

Again,  beds  have  been  uplifted  and  pressed  into  great  folds, 
and  thus  mountain-ranges  have  sometimes  been  made.  They 
have  often,  in  addition,  undergone  crystallization  over  areas 
thousands,  or  even  hundreds  of  thousands,  of  square  miles  in 
extent,  the  original  mud-bed  becoming  in  the  change  a  rock 


INTRODUCTION.  3 

like  gneiss  or  granite.  Thus  also  the  disturbances  or  great 
movements  in  the  earth's  crust  are  registered,  and  the  various 
steps  in  the  progress  may  be  deciphered. 

The  succession  of  rocks  in  the  earth's  crust  is,  hence,  like 
a  series  of  historical  volumes,  full  of  inscriptions.  It  is  the 
endeavor  of  Geology  to  examine  and  interpret  these  inscrip- 
tions. They  are  sufficient,  if  faithfully  studied  and  compared, 
to  make  known  the  progress  of  the  growing  continents  through 
all  the  successive  periods  in  their  long  history. 

3.  Facts  taught  by  the  fossil  contents  of  rocks.  —  Again, 
most  of  the  beds  contain  shells,  corals,  leaves,  and  other  re- 
lated forms,  called  fossils,  —  so  named  because  dug  out  of  the 
earth,  the  word  being  from  the  Latin  fossilis,  meaning,  that 
which  is  dug  up.     These  fossils  are  the  remains  of  animals  or 
plants  once  alive  over  the  earth.     The  shells  and  corals  were 
formed  by  animals,  just  as  the  shell  of  a  clam  is  now  formed 
by  the  animal  occupying  it,  or  corals  of  existing  seas  by  the 
coral  animals.     The  various  species  that  have  left  their  re- 
mains in  any  bed  must  have  been  in  existence  when   that 
bed   was   in   process   of   formation :    they   were   the   living 
species  of  the  waters  and  land  at  the  time. 

The  fossils  that  occur  in  one  range  of  beds  differ  more  or 
less  in  species  from  those  of  the  next  above  in  the  series ;  and 
those  of  this  range  of  beds  are  unlike  those  of  the  following ; 
and  so  on.  Since,  therefore,  each  bed  contains  evidence  as  to 
what  animals  and  plants  were  living  when  it  was  forming, 
the  study  of  the  fossils  of  the  successive  beds  is  the  study  of 
the  succession  of  living  species  that  haw  existed  in  the  earth's 
history. 

4.  Objects   of  Geology,  and   subdivisions   of  the  science. — 
The  preceding  explanations  afford  an  idea  of  the  objects  of 
the  science  of  Geology.     They  are, — 

1.  To  study  out  the  system  in  the  earth's  features. 

2.  To  ascertain  the  nature  and  arrangement  of  the  rocks. 

3.  To  gather  from  the  rocks  the  successive  events  in  the 
progress  of  the  sphere,  and  present  the  facts  as  a  continuous 


4  INTRODUCTION. 

history ;  part  of  these  facts  pertaining  to  rock-making,  moun- 
tain-making, valley-making,  and  other  operations  connected 
with  the  growth  and  finishing  of  the  continents;  part  to 
changes  in  the  climate,  oceanic  currents,  and  other  physical 
conditions  of  the  earth;  and  part,  to  the  unfolding  of  the 
kingdoms  of  life,  or  the  succession  in  the  plants  and  animals 
of  the  globe. 

4.  To  determine  the  causes  of  all  that  has  happened  in 
the  earth's  history,  that  it  may  be  understood  how  rocks 
were  made,  fractured,  uplifted,  folded,  and  crystallized ;  how 
mountains  were  made,  and  valleys,  and  rivers ;  how  con- 
tinents and  oceanic  basins  were  made,  and  how  altered  in 
size  or  outline  from  period  to  period;  why  the  climate  of 
the  globe  changed  from  time  to  time ;  and  how  the  living 
species  of  the  globe  were  exterminated,  or  otherwise  affected 
by  the  physical  changes  in  progress. 

There  are,  hence,  four  principal  branches  of  the  science  :  — 

1.  Physiographic  Geology,  —  treating  of  the  earth's  phys- 
ical features ;  that  is,  of  the  system  in  the  exterior  features 
of  the  earth.     This  department  properly  includes,  also,  the   - 
system   of  movements   in  the   water  and   atmosphere,  and 
the  system  in  the  earth's  climates,  and  in  the  other  physical 
agencies  or  conditions  of  the  sphere. 

2.  Lithological   Geology,  —  treating    of  the    rocks    of  the 
globe,  their  kinds,  structure,  and   conditions   or   modes   of 
occurrence.     The  word  lithological  is  from  the  Greek  X/0os, 
stone,  and  Xoyo?,  discourse. 

3.  Historical  Geology,  —  treating  of  the  succession  in  the 
rocks  of  the  globe,  and  their  teachings  with  regard  to  the 
successive  conditions  of  the  earth,  or  to  the  changes  in  its 
oceans,  continents,  climates,  and  life. 

4.  Dynamical   Geology,  —  treating   of  the   causes,   or  the 
methods,  by  which  the  rocks  were  made,  and  by  which  all 
the   earth's   changes   were    brought    about.     The   word   dy- 
namical is  from  the  Greek  Si/m/us,  power  or  force. 


PART   I. 
PHYSIOGRAPHIC    GEOLOGY. 


UNDER  the  department  of  Physiographic  Geology  only  a 
brief  and  partial  review  is  here  made  of  the  general  features 
of  the  earth's  surface. 

THE    EARTH'S    FEATURES. 
1.  General  Characteristics. 

1.  Size  and  form.  —  The  earth  has  a  circumference  of  about 
25,000  miles.     Its  form  is  that  of  a  sphere  flattened  at  the 
poles,  the  equatorial  diameter  (7,926  miles)  being  about  26 \ 
miles  greater  than  the  polar. 

2.  Oceanic  basin  and  continental  plateaus,  —  Nearly  three, 
fourths  (more  accurately,  eight  elevenths}  of  the  whole  surface 
are  depressed  below  the  rest,  and  occupied  by  salt  water. 
This  sunken  part  of  the  crust  is  called  the  oceanic  basin,  and 
the  large  areas  of  land  between,  the  continents,  or  continental 
plateaus.  , 

3.  Subdivisions  and  relative  positions  of  the  oceanic  basin  and 
continental  plateaus.  —  Nearly  three  fourths  of  the  area  of  the 
continental  plateaus  are  situated  in  the  northern  hemisphere, 
and  more  than  three  fourths  of  the  oceanic  basin  in  the  south- 
ern hemisphere.     The  dry  land  may  be  said  to  be  clustered 
about  the  North  Pole,  and  to  stretch  southward  in  two  masses, 
an  Oriental,  including  Europe,  Asia,  Africa,  and  Australasia, 
and  an  Occidental,  including  North  and  South  America.     The 
ocean  is  gathered  in  a  similar  manner  about  the  South  Pole, 


6  PHYSIOGRAPHIC   GEOLOGY. 

and  extends  northward  in  two  broad  areas  separating  the  Oc- 
cident and  Orient,  namely,  the  Atlantic  and  Pacific  Oceans, 
and  also  in  a  third,  the  Indian  Ocean,  separating  the  southern 
prolongations  of  the  Orient,  namely,  Africa  and  Australasia. 

The  Orient  is  made,  by  this  means,  to  have  two  southern 
prolongations,  while  the  Occident,  or  America,  has  but  one. 
This  double  feature  of  the  Orient  accords  with  its  great 
breadth ;  for  it  averages  6,000  miles  from  east  to  west,  which 
is  far  more  than  twice  the  mean  breadth  of  the  Occident 
(2,200  miles). 

The  inequality  of  the  two  continental  masses  has  its  paral- 
lel in  the  inequality  of  the  Pacific  and  Atlantic  Oceans ;  for 
the  former  (6,000  miles  broad)  is  more  than  double  the  aver- 
age breadth  of  the  latter  (2,800  miles).  Thus,  there  is  one 
Iroad  and  one  narrow  continental  mass,  and  one  broad  and  one 
narrow  oceanic  area. 

The  connection  of  Asia  with  Australia,  through  the  inter- 
vening islands,  is  very  similar  to  that  of  North  America  with 
South  America.  The  southern  continent,  in  each  case,  lies 
almost  wholly  to  the  east  of  the  meridians  of  the  northern ; 
and  the  islands  between  are  nearly  in  corresponding  posi- 
tions,—  Florida  in  the  Occident  corresponding  to  Malacca 
in  the  Orient,  Cuba  to  Sumatra,  Porto  Eico  to  Java,  and  the 
more  eastern  Antilles  to  Celebes  and  other  adjoining  islands. 
It  is,  therefore,  plain  that  Australia  bears  the  same  relation 
to  Asia  that  South  America  does  to  North  America.  It  is 
also  true  that  Africa  is  essentially  in  a  similar  position  with 
reference  to  Europe. 

The  northern  portion  of  the  Orient,  or  Europe  and  Asia 
combined,  makes  one  continental  area ;  and  its  general  course 
is  east  and  west.  The  northern  portion  of  the  Occident,  or 
North  America,  is  elongated  from  north  to  south. 

4.  Oceanic  depression  and  continental  elevations.  —  The  depth 
of  the  oceanic  basin  below  the  water-level  is  possibly  in 
some  parts  40,000  feet.  The  mean  depth  is  much  less.  The 
depth  across  from  Newfoundland  to  Ireland,  along  what  is 


THE  EARTH'S  FEATURES.  7 

called  the  telegraphic  plateau,  is  from  6,000  to  15,000  feet. 
Farther  south  the  depth  of  the  North  Atlantic  is  mostly  12,000 
to  19,000  feet ;  eighty  miles  from  Bermuda  it  is  25,500  feet. 
The  mean  depth  of  the  North  Pacific,  between  Japan  and  San 
Francisco,  has  been  determined  by  Professor  Bache,  from  the 
passage  of  earthquake-waves  in  1855,  to  be  13,000  feet;  and 
that  of  the  South  Pacific,  between  South  America  and  New 
Zealand,  on  similar  evidence,  is  about  the  same. 

The  highest  point  of  the  continents  that  has  been  measured 
is  29,000  feet :  it  is  the  peak  called  Mount  Everest,  in  the 
Himalayas.  But  the  mean  height  of  the  continental  plateaus 
is  only  about  1,000  feet.  The  mean  height  of  the  several 
continents  has  been  estimated  as  follows :  Of  Europe,  670 
feet ;  Asia,  1,150  feet ;  North  America,  748  feet ;  South 
America,  1,132  feet ;  all  America,  932  feet ;  Europe  and  Asia, 
1,000  feet ;  Africa,  probably  1,600  feet ;  and  Australia,  per- 
haps 500.  The  material  in  the  Pyrenees,  if  spread  equally 
over  Europe,  would  raise  the  surface  only  6  feet ;  and  that 
of  the  Alps,  only  22  feet.  Although  some  mountain-chains 
reach  to  a  great  elevation,  their  breadth  above  a  height  of 
1,000  feet  is  small  compared  with  that  of  the  continents 
below  this  height. 

5.  True  outline  of  the  oceanic  depression.  —  Along  the 
oceanic  borders  the  sea  is  often,  for  a  long  distance  out,  quite 
shallow,  because  the  continental  lands  continue  on  under 
water  with  a  nearly  level  surface ;  then  comes  a  rather  sud- 
den slope  to  the  deep  bed  of  the  ocean.  This  is  the  case  off 
the  eastern  coast  of  the  United  States,  east  and  south  of  New 
England.  Off  New  Jersey  the  deep  water  begins  along  a 
line  about  80  miles  from  the  shore ;  off  Virginia  this  line  is 
50  to  60  miles  at  sea ;  and  thus  it  gradually  approaches  the 
coast  to  the  southward.  The  slope  of  the  bottom,  for  the  80 
miles  off  New  Jersey,  is  only  1  foot  in  700  feet.  The  true 
boundary  between  the  continental  plateau  and  the  oceanic 
depression  is  the  commencement  of  the  abrupt  slope.  The 
British  Islands  are  situated  on  a  submerged  portion  of  the 


8  PHYSIOGRAPHIC  GEOLOGY. 

European  continent,  and  are  essentially  a  part  of  that  con- 
tinent, the  limit  of  the  oceanic  basin  being  far  outside  of 
Ireland,  and  extending  south  into  the  Bay  of  Biscay.  New 
Guinea  is  in  a  similar  way  proved  to  be  a  part  of  Australia. 

6.  Surfaces  of  the  continents.  —  The  surface  of  a  continent 
comprises  (1)  low  lands,  (2)  plateaus  or  table-lands,  and  (3) 
mountain-ridges.  The  mountain-ridges  may  rise  either  from 
the  low  lands  or  the  plateaus.  The  plateaus  are  great  areas 
of  the  surface  situated  several  hundred  feet,  or  a  thousand 
feet  or  more,  above  the  sea,  or  above  the  general  level  of 
the  low  lands.  They  are  often  parts  of  the  great  moun- 
tain-chains. Sometimes  plateaus  include  a  region  between 
mountain-ridges,  and  sometimes  the  mass  of  the  mountains 
themselves  out  of  which  the  ridges  rise.  For  example,  the 
regions  of  Northern  and  Southern  New  York  are  plateaus  (the 
former  averaging  1,500  feet  in  height,  the  latter  2,000  feet) 
situated  within,  or  on  the  borders  of,  the  Appalachian  chain. 
Between  the  Sierra  Nevada  and  the  Wahsatch  there  is  a 
plateau  of  vast  extent,  having  the  Great  Salt  Lake  in  its 
northeastern  portion ;  its  height  above  the  sea  averages  4,000 
feet;  the  high  ranges  of  the  Humboldt  mountains  rise  out 
of  it.  The  eastern  part  of  New  Mexico  is  a  plateau  of  about 
the  same  elevation,  called  the  Llano  Estacado ;  and  Mexico 
is  situated  in  another,  from  which  rise  various  ridges  and 
peaks.  The  Desert  of  Gobi,  between  the  Altai  and  the  Kuen- 
Lun  range,  is  a  desert  plateau  about  4,000  feet  high,  while 
the  plateau  of  Thibet,  between  the  Kuen-Lun  range  and  the 
Himalayas,  is  11,500  to  13,000  feet  above  the  sea.  Persia 
and  Armenia  constitute  another  plateau.  These  examples  are 
sufficient  to  explain  the  use  of  the  term. 

2.  System  in  the  Earth's  Features. 

1.  General  form  of  the  continents  resulting  from  their  reliefs. 
—  The  continents  are  constructed  on  a  common  model,  as 
follows  :  they  have  high  borders  and  a  low  centre,  and  are, 


THE  EARTH'S   FEATURES.  9 

therefore,  basin-shaped.  Thus,  North  America  has  the  Appa- 
lachians on  the  eastern  border,  the  Eocky  chain  on  the  west, 
and  between  these  the  low  Mississippi  basin.  Fig.  1  illus- 


Fig.  1. 


trates  this  form  of  the  continent.  In  the  section,  b  represents 
the  Rocky  Mountain  chain  on  the  west,  with  its  double  line 
of  ridges  at  summit ;  a,  the  Washington  chain  (including  the 
Sierra  Nevada  and  Cascade  range),  near  the  Pacific  coast ;  c, 
the  Mississippi  basin ;  d,  the  Appalachian  chain  on  the  east. 
South  America,  in  a  similar  manner,  has  the  Andes  on  the 
west,  the  Brazilian  Mountains  on  the  east,  and  other  heights 
along  the  north,  with  the  low  region  of  the  Amazon  and  La 
Plata  making  up  the  larger  part  of  the  great  interior.  Fig.  2 

Fig.  2. 


is  a  transverse  section  from  west  to  east  (W,  E),  showing  the 
Andes  at  a,  and  the  Brazilian  Mountains  at  b.  In  these 
sections  the  height  as  compared  with  the  breadth  is  neces- 
sarily much  exaggerated. 

In  the  Orient  there  are  mountains  on  the  Pacific  side, 
others  on  the  Atlantic;  and,  again,  the  Himalayas,  on  the 
south,  face  the  Indian  Ocean,  and  the  Altai  face  the  Arctic  or 
Northern  Seas.  Between  the  Himalayas  (or  rather  the  Kuen- 
Lun  Mountains,  which  are  just  north)  and  the  Altai,  lies  the 
plateau  of  Gobi,  which  is  low  compared  with  the  enclosing 
mountains  ;  and  farther  west  there  are  the  low  lands  of  the 
Caspian  and  Aral,  the  Caspian  lying  even  below  the  level  of 
the  ocean.  The  Urals  divide  the  6,000  miles  of  breadth  into 
i* 


10  PHYSIOGRAPHIC   GEOLOGY. 

two  parts,  and  so  give  Europe  some  title  to  its  designation 
as  a  separate  continent.  West  of  their  meridian  there  are 
again  extensive  low  lands  over  Middle  and  Southern  Euro- 
pean Eussia. 

In  Africa  there  are  mountains  on  the  eastern  border,  and 
on  the  western  border  south  of  the  coast  of  Guinea ;  there  are 
also  the  Atlas  Mountains  along  the  Mediterranean,  and  the 
Kong  Mountains  along  the  Guinea  coast;  and  the  interior 
is  relatively  low,  although  mostly  1,000  to  2,000  feet  in  ele- 
vation. 

In  Australia,  also,  there  are  high  lands  on  the  eastern  and 
western  borders,  and  the  interior  is  low. 

All  the  continents  are,  therefore,  constructed  on  the  basin- 
like  model 

2.  Relation  between  the  heights  of  the  borders  and  the  extent 
of  the  adjoining  ocean.  —  There  is  a  second  great  truth  with 
regard  to  the  continental  reliefs;  namely,  that  the  highest 
border  faces  th#  largest  ocean. 

By  largest  ocean  is  meant  not  merely  greatest  in  surface, 
but  greatest  in  capacity,  the  depth  being  important  in  the 
consideration.  The  Pacific,  both  in  depth  and  surface,  greatly 
exceeds  the  Atlantic ;  so  the  South  Pacific  exceeds  the  North 
Pacific,  and  the  South  Atlantic  exceeds  the  North  Atlantic. 
The  Indian  Ocean  is  also  one  of  the  large  oceans ;  for  it  ex- 
tends eighty  degrees  of  latitude  south  of  Asia,  before  reaching 
any  body  of  Antarctic  land ;  and  this  is  equivalent  to  5,500 
miles,  nearly  the  mean  breadth  of  the  Pacific :  moreover,  as 
it  is  much  more  free  from  islands  than  the  Pacific,  it  is 
probably  the  deeper,  of  the  two,  and,  consequently,  yields  in 
capacity  to  no  other  ocean  on  the  globe. 

Each  of  the  continents  sustains  the  truth  announced. 
North  America  has  its  great  mountains,  the  Eocky  chain,  on 
the  side  of  the  great  ocean,  the  Pacific ;  and  its  small  moun- 
tains, the  Appalachian,  on  the  side  of  the  small  ocean.  So, 
South  America  has  its  highest  border  on  the  west ;  and  the 
Andes  as  much  exceed  in  elevation  and  abruptness  the  Eocky 


THE  EARTH'S  FEATURES.  11 

chain  as  the  South  Pacific  exceeds  in  capacity  the  North 
Pacific.  The  Orient  has  high  ranges  of  mountains  on  the 
east,  or  the  Pacific  side,  and  lower,  as  those  of  Norway  and 
other  parts  of  Europe,  on  the  west ;  and  the  Himalayas,  the 
highest  of  the  globe,  face  the  great  Indian  Ocean  (besides 
being  most  elevated  eastward  toward  the  great  Pacific),  while 
the  smaller  Altai  face  the  small  Northern  Ocean.  In  Africa 
the  eastern  mountains,  or  those  on  the  side  of  the  Indian 
Ocean,  are  higher  than  those  on  that  of  the  Atlantic.  In 
Australia  the  highest  border  is  on  the  Pacific  side ;  for  the 
South  Pacific,  taking  into  view  its  range  in  front  of  East 
Australia,  is  greater  than  the  Indian  Ocean  fronting  West 
Australia. 

Hence  the  basin-like  shape  before  illustrated  is  that  of  a 
basin  with  one  border  much  higher  than  the  other ;  and  with 
the  highest  border  on  the  side  adjoining  the  largest  ocean. 

These  features  have  a  vast  influence  in  adapting  the  con- 
tinents for  man. 

America  stands  with  its  highest  border  in  the  far  west,  and 
with  all  its  great  plains  and  great  rivers  inclined  toward  the 
Atlantic ;  for,  through  the  Gulf  of  Mexico,  the  whole  interior, 
as  well  as  the  eastern  border,  has  its  natural  outlet  eastward. 
Had  the  high  mountains  of  the  continent  been  placed  on  its 
eastern  side,  they  would  have  condensed  the  moisture  of  the 
winds  before  they  had  traversed  the  land,  and  sent  it  back,  in 
hurrying  and  almost  useless  torrents,  to  the  ocean ;  but,  being 
on  the  western,  all  the  slopes,  from  the  Atlantic  to  the  tops  of 
the  Eocky  Mountains,  lie  open  to  the  moist  winds,  and  fields 
and  rivers  show  the  good  they  thus  receive. 

Again,  the  Orient,  instead  of  rising  into  Himalayas  on  the 
Atlantic  border,  has  its  great  heights  in  the  remote  east,  and 
its  vast  plains  and  the  larger  part  of  its  great  rivers,  even 
those  of  Central  Asia,  have  their  natural  outlet  westward,  or 
toward  the  same  Atlantic  Ocean.  Thus,  as  Professor  Guyot 
has  said,  the  vast  regions  of  the  world  which  are  best  fitted 


12  PHYSIOGRAPHIC  GEOLOGY. 

by  climate  and  productions  for  man  are  combined  into  one 
great  arena  for  the  progress  of  civilization.  Both  the  Orient 
and  the  Occident  pour  their  streams  and  bear  a  large  part  of 
their  commerce  into  a  common  ocean;  and  this  ocean,  the 
Atlantic,  is  but  a  narrow  ferriage  between  them,  and  vastly 
better  for  the  union  of  nations  than  connection  by  as  much 
dry  land :  3,000  miles  of  dry  land  would  be,  even  in  the 
present  age,  a  serious  obstacle  to  intercourse ;  while  3,000 
miles  of  ocean  draw  the  east  and  west  only  into  closer 
political,  commercial,  and  social  relations. 


PART  II. 

LITHOLOGICAL    GEOLOGY. 


THE  term  rock,  in  geology,  is  applied  to  all  natural  for- 
mations of  rock-material,  whether  solid  or  otherwise.  Not 
only  are  sandstones  and  slates  called  rocks,  but  also  the 
loose  earth,  sand,  and  gravel  of  the  surface,  provided  they 
have  been  laid  out  in  beds  ly  natural  causes.  All  sand- 
stones were  once  beds  of  loose  sand;  and  there  is  every 
shade  of  gradation,  from  the  hardest  sandstone  to  the 
softest  sand-bed :  so  that  it  is  impossible  to  draw  a  line 
between  the  consolidated  and  unconsolidated.  Geology  does 
not  attempt  to  draw  the  line,  but  classes  all  together  as 
rocks,  regarding  consolidation  as  an  accident  that  might  or 
might  not  happen  in  the  case  of  the  earth's  beds  or  de- 
posits. 

Kocks  may  be  studied  simply  as  rocks,  —  that  is,  with 
reference  to  their  composition,  —  and  collections  may  be 
made  containing  specimens  of  their  various  kinds.  Again, 
they  may  be  studied  as  rock-masses  spread  out  over  the 
earth  and  forming  the  earth's  crust ;  and,  with  this  in  view, 
the  condition,  structure,  and  arrangement  of  the  great  rock- 
masses  (called  sometimes  terranes)  would  come  up  for  con- 
sideration. The  two  subjects  under  Lithological  Geology 
are,  therefore:  1.  The  Constitution  of  Rocks;  2.  The  Con- 
dition, Structure,  and  Arrangement  of  Rock-masses,  or  Ter- 
ranes. 


14  LITHOLOGICAL   GEOLOGY. 

I.  — CONSTITUTION    OP    ROCKS. 
1.  General  Observations  on  their  Constituents. 

Eocks  consist  essentially  of  minerals,  and  the  minerals  of 
the  common  rocks  are  of  four  groups  :  — 

1.  Quartz,  or,  as  it  is  called  in  chemistry,  silica. 

2.  Silicates,  or  compounds  of  silica  and  other  substances. 

3.  Carbon,  the  chief  element  of  charcoal,  with  carbonic  acid 
and  mineral  coal. 

4.  Carbonates,  or  compounds  of  carbonic  acid  and  other 
substances. 

1.  Quartz,  or  Silica.  —  Quartz,  or  silica  (consisting  of  sili- 
cium  and  oxygen),  far  exceeds  all  other  species  in  abundance. 
It  is  one  of  the  hardest  of  common  minerals ;  it  does  not 
melt  before  the  blow-pipe ;  it  does  not  dissolve  in  water. 
Its  hardness  and  durability  especially  fit  it  for  this  place 
of  first  importance  in  the  material  of  the  earth's  founda- 
tions. 

It  is  often  seen  in  crystals  of  the  forms  represented  in  Figs. 

3,  4,  though  generally  occurring  in  grains,  pebbles,  or  masses. 

It  is  distinguished  ordinarily  by  its  glassy 

Fig.  3.          Fig.  4.  ,  ^.  ,  -11  j 

aspect,  whitish  or  grayish  color,  and  an 
absence  of  all  tendency  to  break  with  a 
smooth  surface  of  fracture  (a  quality  of 
crystals  called  cleavage).  Although  usually 
nearly  colorless  or  white,  it  is  very  often 
reddish,  yellowish,  brownish  (especially 
smoky  brown),  and  even  black ;  and  the  lustre  is  sometimes 
very  dull,  as  in  chalcedony,  flint,  and  jasper.  The  sands  and 
pebbles  of  the  sea-shores  and  gravel-beds  are  mostly  quartz, 
—  because  quartz  resists  the  wearing  action  of  waters  better 
than  any  other  common  mineral.  For  the  same  reason,  most 
sandstones  and  conglomerates  consist  mainly  of  quartz. 

The  hardness  (on  account  of  which  it  scratches  glass 
easily),  infusibility,  insolubility,  non-action  of  acids,  and 


CONSTITUTION   OF  ROCKS.  15 

absence  of  cleavage  are  the  characters  that  serve  to  distin- 
guish quartz  from  the  other  ingredients  of  rocks. 

Although  quartz  is  one  of  the  original  minerals  of  the 
earth's  crust,  the  quartz  of  rocks  is  not  all  directly  of  mineral 
origin.  Part  of  it  has  passed  through  living  beings,  either 
plants  or  animals ;  for  some  of  the  lowest  species  of  these 
kingdoms  of  life  have  the  power  of  making  siliceous  shells 
or  forming  siliceous  particles  or  spicules  in  their  texture ;  and 
beds  have  been  made  of  these  microscopic  siliceous  shells  and 
spicules.  The  animal  species  that  secrete  spicules  of  silica 
are  the  Sponges;  and  those  making  siliceous  shells  are  the 
microscopic  forms  called  Polycystines.  The  plants  making 
siliceous  shells  are  the  microscopic  kinds  called  Diatoms. 
(See  page  61.) 

2.  Silicates.  —  Silica  also  occurs  in  many  of  the  other  rock- 
making  minerals,  constituting  what  are  called  silicates.  It 
exists,  thus,  in  combination  with  the  constituents  of  the  bases 
alumina,  magnesia,  lime,  potash,  soda,  the  oxides  of  iron,  and  a 
few  others. 

Pure  alumina  (consisting  of  aluminum  and  oxygen),  the 
most  important  of  the  above-mentioned  bases,  is  hard,  infusi- 
ble, and  insoluble,  and  therefore  adapted  to  be  next  in  abun- 
dance to  silica.  When  crystallized,  it  is  the  hardest  of  all 
known  substances,  excepting  the  diamond,  it  being  the  gem 
sapphire.  A  massive  or  rock-like  variety,  reduced  to  powder, 
is  emery. 

Magnesia  (magnesium  and  oxygen),  well  known  under  the 
form  of  calcined  magnesia,  is  as  hard  as  quartz,  when  crystal- 
lized, and  equally  infusible  and  insoluble. 

Lime  (calcium  and  oxygen)  is  common  quick-lime.  Potash 
(potassium  and  oxygen)  and  soda  (sodium  and  oxygen)  are 
the  alkalies  ordinarily  so  called.  These  three  ingredients,  or 
their  elements,  are  found  in  many  silicates.  The  same  is  true, 
for  the  most  part,  of  the  oxides  of  iron.  The  compounds  of 
silica  and  alumina  alone  are  infusible  ;  but  when  lime,  potash, 
soda,  or  an  oxide  of  iron  is  present,  the  silicate  is  fusible  ;  and 


16  LITHOLOGICAL   GEOLOGY. 

this  fits  them  for  being  the  constituents  of  igneous  or  volcanic 
rocks. 

The  following  are  the  most  common  of  these  silicates  :  — 

1.  Feldspar.  —  Feldspar   consists   of  silica   and   alumina, 
along  with  lime,  potash,  or  soda.     Common  feldspar,  or  ortho- 
clase,  contains  mainly  potash,  along  with  the  silica  and  alu- 
mina; albite  contains,  in  place   of  the   potash,  soda;   and 
labradorite,  oligoclase,  and  other  kinds  of  feldspar  contain  lime 
as  well  as  soda.     The  specific  gravity  is  2.4-2.7. 

Either  of  these  kinds  of  feldspar  is  distinguished  from 
quartz  by  having  a  distinct  cleavage-structure,  the  grains 
or  masses  breaking  easily  in  two  directions  with  a  flat  and 
shining  surface.  They  are  nearly  as  hard  as  quartz,  often 
white,  but  sometimes  flesh-red.  The  albite  is  usually  white, 
and  the  labradorite  often  brownish,  with  often  a  beautiful 
play  of  colors. 

2.  Mica,  —  Mica  consists  of  silica  and  alumina,  along  with 
potash,  lime,  magnesia,  or  oxide  of  iron.     It   cleaves  easily 
into    tough  leaves,   thinner  than  the   thinnest  paper,   and 
somewhat  elastic.     On  account  of  its  transparency,  and  its 
difficult  fusibility,  it  is  often  used  in  the  doors  of  stoves.     Its 
most  common  colors  are  whitish,  brownish,  and  black.     Some 
micas  contain  water,  that  is,  are  hydrous ;  and  these  hydro- 
micas,  as  they  are  called,  are  pearly  in  lustre,  feel  a  little 
soapy  to  the  fingers,  and  are  sometimes  mistaken  for  talc. 

The  minerals  quartz,  feldspar,  and  mica  are  the  con- 
stituents of  granite;  and  they  may  be  distinguished  in  it 
as  follows :  the  grains  of  quartz,  by  their  more  glassy  lus- 
tre, grayer  color,  and  want  of  cleavage ;  the  grains  of  feld- 
spar, by  their  cleavage ;  the  grains  of  mica,  by  their  very 
easy  cleavage  into  thin,  elastic  leaves  by  means  of  the  point 
of  a  knife-blade. 

3.  Hornblende  and  Pyroxene.  —  Hornblende  and  pyroxene 
consist,  alike,  of  silica  along  with  magnesia,  lime,  and  pro- 
toxide of  iron.     They  are  both  of  dark-green,  greenish-black, 
and  black   colors   in   most   of  the   rocks   formed   of  them, 


CONSTITUTION   OF   ROCKS. 


17 


though  sometimes  gray  and  white.  Both  are  cleavable ;  but, 
unlike  mica,  they  are  brittle,  and  never  afford  flexible  or  elas- 
tic folia  by  cleavage.  Hornblende  often  occurs  in  slender 
needle-shaped  crystals ;  and  there  are  fibrous  varieties  of  each, 
called  asbestus.  They  are  nearly  as  hard  as  feldspar,  but 
much  heavier  than  it  (specific  gravity  =  2.8-3.5),  and  in 
general  much  more  fusible. 

4.  Garnet ;  Tourmaline  ;  Andalusite.  —  These  are  other 
silicates,  of  very  common  occurrence  in  rocks.  They  are 
usually  found  in  crystals  distributed  through  a  rock.  Gar- 
net is  commonly  in  dark-red,  brownish,  or  black  crystals 
of  12  or  24  sides  (dodecahedrons  or  trapezohedrons).  The 


Fig.  5. 


Fig.  6. 


Fig.  7. 


first  of  these  forms  is  represented  in  Fig.  5,  showing  garnets 

distributed  through  a  mica  schist.     Tourmaline  is  generally 

in  oblong  3,  6,  9,  or  12  sided  crystals,  shining  and  black ; 

also  at  times  blue-black,  brown, 

green,    and   red.      The  crystals 

are  common  in  gneiss  and  mica 

schist,  and  are  at  times  imbedded 

in  quartz  (Fig.  6).    Andalusite  is 

found  in  imbedded  crystals  in 

clay  slate :  the  form  is  nearly  a 

square  prism.     The  interior  of 

the  crystals  is  very  frequently 

black    or    grayish-black  at  the 

centre  and  angles  (Fig.  7),  while  the  rest  is  nearly  white ;  and 

this  variety  is  called  made,  or  chiastolite. 


18  LITHOLOGICAL   GEOLOGY. 

5.  Talc  ;  Serpentine.  —  Talc  and  serpentine  are  com- 
pounds of  silica  and  magnesia  with  water.  They  both  have 
a  greasy  feel,  —  especially  the  talc.  Talc  is  a  very  soft  min- 
eral, so  soft  that  it  does  not  feel  gritty  to  the  teeth.  It  is 
often  in  foliated  plates  or  masses  like  mica ;  but  the  folia, 
or  leaves,  though  separating  rather  easily,  and  flexible,  are 
not  elastic.  The  usual  color  is  pale  green.  A  massive  gran- 
ular talc,  of  whitish,  grayish,  or  greenish  color,  is  called  soap- 
stone,  or  steatite. 

Serpentine  is  harder  than  talc.  It  is  usually  a  dark-green 
massive  rock,  of  a  very  fine-grained  texture.  It  may  be  cut 
with  a  knife,  and  it  differs  in  this,  and  also  in  its  being 
lighter,  from  compact  hornblendic  rocks. 

3.  Carbon,  Mineral  Coal,  Carbonic  Acid.  —  1.  Carbon.  Car- 
bon is  familiarly  known  under  three  names  and  conditions : 
/.  Diamond;  2.  Graphite;  8.  Charcoal.  The  second  is  the  ma- 
terial of  lead-pencils,  and  is  called  also  black  lead,  though 
containing  no  lead.  The  diamond  is  the  hardest  of  all 
known  substances,  and  graphitey  one  of  the  softest.  Char- 
coal is  carbon  combined  with  a  little  oxygen  and  hydrogen ; 
it  is  derived  from  wood  by  smothered  combustion,  and  is  not 
known  among  minerals. 

2.  Mineral  CoaL  —  Mineral  coal  is  carbon  combined  with 
some  hydrogen  and  oxygen.     Like  charcoal,  mineral  coal  was 
made  from  wood  or  plants.     The  variety  burning  with  a  bright 
flame  is  called  bituminous  coal     The  harder  kind,  burning  with 
a  feeble  flame,  bluish  or  yellowish,  is  anthracite.     Broiun  coal 
differs  from  true  bituminous  coal  in  containing  more  oxygen 
(20  per  cent  or  more)  and  giving  a  brownish-black  powder, 
and  also  in  coming  from  strata  newer  than  those  of  the  Car- 
boniferous age.    Lignite  is  a  brown  coal  retaining  in  part  the 
structure  of  the  original  wood,  and  having  an  empyreumatic 
odor  when  burned. 

3.  Carbonic  Acid  is  a  gas  consisting  of  carbon  and  oxygen. 
It  composes  about  4  parts  by  volume  of  10,000  parts  of  the 
atmosphere.     It  is  formed  in  all  combustion  of  wood  or  coal, 
and  is  given  out  in  the  respiration  of  animals. 


CONSTITUTION  OF  ROCKS. 


19 


4.  Carbonates. — 1.  Carbonate  of  Lime,  or  Calcite,  the  essential 
ingredient  of  limestone  and  marble,  consists  of  carbonic  acid 
and  lime.  It  crystallizes  in  a  great  variety  of  forms,  a  few  of 
which  are  represented  in  Figs.  8,  9.  It  cleaves  easily  in  three 
directions  with  bright  surfaces,  as  may  be  seen  on  exam- 
ining even  the  grains  of  a  fine  white  marble.  It  is  rather 
soft,  so  as  to  be  easily  scratched  with  a  knife ;  dissolves  in 
diluted  acid  (chlorohydric)  with  effervescence,  that  is,  with 
an  escape  of  carbonic  acid  gas;  and  when  heated  (as  in  a 
lime-kiln  or  before  the  blow-pipe)  it  burns  to  quick-lime 
without  melting.  By  its  effervescence  with  acids  it  differs 
from  all  the  minerals  before  mentioned. 


2.  Dolomite  is  a  carbonate  of  lime  and  magnesia ;  that  is, 
it  differs  from  calcite  in  containing  magnesia  in  place  of 
part  of  the  lime.  Much  of  the  so-called  limestone  of  the 
world  is  magnesian  limestone.  It  closely  resembles  common 
limestone,  but  may  be  distinguished  by  its  effervescing  scarcely 
at  all  with  acid  unless  heat  be  applied.  The  trial  may  be 
made  by  dropping  a  particle,  as  large  as  half  a  grain  of  wheat, 
into  a  test-glass  containing  a  mixture,  half  and  half,  of  chloro- 
hydric acid  and  water. 

The  larger  part  of  the  carbonate  of  lime  of  rocks  has  been 
derived  directly  from  shells,  corals,  and  other  animal  re- 
mains. Animals  take  the  material  of  their  shells  and  other 
stony  structures  from  the  waters  of  the  globe,  or  from  the 


20  LITHOLOGICAL   OEOLOGY. 

food  they  eat,  through  their  power  of  secretion,  —  the  same 
power  by  which  man  forms  his  bones.  After  death  the  shells, 
corals,  or  bones,  which  are  of  ho  further  use  to  the  species, 
are  turned  over  to  the  mineral  kingdom  to  be  made  into  rocks. 
The  immense  extent  and  thickness  of  the  earth's  limestone 
rocks,  nearly  all  of  which,  the  magnesian  included,  are  proba- 
bly of  organic  origin,  give  some  idea  of  the  amount  of  life 
that  has  lived  and  died  through  past  time.  The  magnesia 
of  the  limestones  containing  it  was  taken  in  chiefly,  if  not 
wholly,  during  the  process  of  consolidation ;  and  it  was  prob- 
ably derived  from  the  ocean's  waters. 

•  Carbonate  of  lime  and  silica  are  the  two  stony  ingre- 
dients which  have  been  contributed  largely  by  living 
species  to  the  earth's  rock-formations.  Mineral  coal  is  an- 
other material  abundantly  contributed  by  the  kingdoms  of 
life,  the  great  beds  of  the  coal  period  and  of  other  eras 
having  been  all  made  from  the  material  of  plants. 

5,  Sand  ;  Clay.  —  Sand  and  clay  are  not  minerals  :  they  are 
mixtures  of  minute  particles  of  different  minerals,  produced 
by  the  wearing  down  of  different  rocks.  A  large  part  of 
common  clay  is  pulverized  feldspar  mixed  with  some  quartz. 
Other  kinds,  having  a  greasy  feel  in  the  fingers,  consist  of 
a  material  derived  from  the  decomposition  of  feldspar  and 
allied  minerals,  and  are  composed  of  alumina,  silica,  and 
water,  mixed  more  or  less  with  quartz  and  other  impurities. 

2.  Kinds  of  Rocks. 

1.  Fragmental  and  Crystalline  Rocks.  —  The  minerals  of 
which  a  rock  consists  may  be  either  (1)  in  broken  or  worn 
grains  or  pebbles,  like  those  of  sand  or  clay,  or  a  bed  of 
pebbles;  or  (2)  they  may  be  in  crystalline  grains,  in  which 
case  they  were  formed  where  they  now  are  at  the  time  of 
the  crystallization  of  the  rock.  Such  crystalline  grains  are 
angular,  and  in  the  case  of  most  minerals  excepting  quartz 
show  surfaces  of  cleavage. 


KINDS  OF  ROCKS.  21 

The  rocks  of  the  first  kind,  consisting  of  fragments  of  other 
rocks,  are  called  fragmental  rocks ;  and  those  of  the  latter 
kind,  crystalline  rocks.  Eocks  made  from  clay,  mud,  or 
sand  are  fragmental  rocks  no  less  than  those  consisting  of 
coarser  material;  for  each  particle  of  the  clay  or  mud  is  in 
general  a  rock-fragment,  however  minute  it  may  be.  Nearly 
all  the  earth  and  clay,  sand-beds  and  pebble-beds,  of  the 
globe  have  been  made  of  material  produced  by  the  wear, 
decomposition,  or  disaggregation  of  rocks. 

Fragmental  rocks  are  often  called  sedimentary  rocks,  be- 
cause formed  in  general  from  sediment,  or  the  earth  deposited 
by  waters  of  the  ocean,  lakes,  or  rivers. 

Intermediate  between  rocks  that  are  obviously  either  frag- 
mental or  crystalline  there  are  others,  of  a  flinty  compactness, 
which  show  no  distinct  grains,  and  are  therefore  not  easily 
referred  to  either  division.  In  the  case  of  such  rocks,  the 
geologist,  in  order  to  determine  the  division  to  which  they 
belong,  has  to  examine  the  rocks  of  the  beds  associated  with 
them.  If  these  associated  rocks  are  fragmental,  then  the 
compact  beds  are  probably  so  also ;  but  if  these  are  crystal- 
line, then  they  are  probably  related  to  the  crystalline.  Expe- 
rience among  rocks  is  required  to  decide  correctly  in  all  such 
cases. 

2.  Metamorphic  and  Igneous  Rocks.  —  The  crystalline  rocks 
are  either  metamorphic  or  igneous. 

1.  Metamorphic  rocks  are  those  which  have  been  altered 
or  metamorphosed  by  means  of  heat.     The  alteration,  when 
most  complete,  consists  in  a  complete  crystallization  of  the 
rock ;  and  when  less  so,  in  a  consolidation  of  it,  with  some- 
times no  distinct  crystallization. 

Earthy  sandstones  and  clay-rocks  have  been  thus  meta- 
morphosed into  granite,  gneiss,  and  mica  schist,  and  ordinary 
limestone  into  statuary  marble. 

2.  Igneous  rocks  are  those  which  have  been  ejected  in  a 
melted  state,  as  from  volcanic  vents,  or  from  fissures  opened 
to  some  seat  of  fires  within  or  below  the  earth's  crust. 


22  LITHOLOGICAL  GEOLOGY. 

3.  Calcareous  rocks.  —  Calcareous  rocks  are  the  limestones. 
To  a  great  extent  they  have  been  formed  from  pulverized 
animal  relics,  such  as  shells  and  corals ;  and  in  this  case  they 
are   properly  fragmental   or   sedimentary  beds,  although   so 
finely  compact  that  this  might  not  be  suspected  from  their 
texture. 

Some  limestones  have  been  made  from  the  accumulation 
and  consolidation  of  very  minute  shells,  called  Rhizopods. 
These  shells  being  no  larger  than  the  finest  grains  of  sand, 
no  powdering  was  necessary.  The  limestone  rocks  formed 
of  them  are  not  fragmental  in  origin. 

Other  calcareous  rocks  have  been  deposited  from  waters 
holding  the  material  in  solution,  and  are,  therefore,  of  chemi- 
cal origin.  Of  this  kind  is  the  travertine  of  Tivoli  near  Eome 
in  Italy,  and  of  Gardiner's  Kiver  in  the  geyser  region  of 
the  Yellowstone  Park,  and  similar  beds  in  many  regions  of 
mineral  springs,  besides  the  petrified  moss  and  trees  of  some 
marshy  places. 

4.  Massive,  schistose,  laminated,  slaty,  shaly  rocks.  —  Eocks 
are  termed  massive  when  there  is  no  tendency  to  break  into 
slabs  or  plates,  as  in  the  case  of  granite  and  most  conglom- 
erates ;  schistose,  when  crystalline  and  breaking  into  slabs  or 
plates,  owing  to  the  arrangement  in  layers  of  the  mineral 
ingredients,  especially  the   mica  or  the   hornblende;   lami- 
nated, when  splitting  into  slabs  or  flagging-stones,  but  not  in 
consequence  of  a  crystalline  structure ;  slaty,  when  dividing 
easily  into  thin,  even,  hard  slates,  like  roofing-slate;  shaly, 
when  dividing  easily  into  thin  plates  like  a  slate-rock,  but 
the  plates  irregular  and  fragile. 

The  term  schist  is  applied  to  a  schistose  rock ;  flag,  to  a 
laminated  rock ;  slate,  to  a  slaty  rock ;  shale,  to  a  shaly  rock. 

A  hydrous  mineral  is  one  containing  water ;  and  a  hydrous 
rock  contains  a  hydrous  mineral  among  its  constituents. 

The  kinds  of  rocks  are  here  described  under  the  four 
heads:  1.  Fragmental  Rocks,  not  calcareous;  2.  Metamorphic 
Eocks,  not  calcareous ;  3.  Calcareous  Rocks ;  4.  Igneous  Rocks. 


KINDS  OF  ROCKS.  23 

I .  Fragmental  Rocks. 

1.  Sandstone,  —  Composed  of  sand,  coarse  or  fine.     When 
of   pure    quartz    sand,   the    rock    is    a    siliceous   sandstone ; 
and  if  very  hard  and  a  little  pebbly,  a  grit.     When  earthy 
or  clayey,  it  is  an  argillaceous  sandstone,  the  term  argilla- 
ceous meaning  clayey.     Argillaceous  sandstones  are  usually 
laminated,  and,  when  very  hard,  may  make  good  flagging- 
stone. 

2.  Conglomerate.  —  Containing  rounded  or  angular  pebbles. 
If  rounded  pebbles,  the  rock  is  often  called  a  pudding-stone  ; 
and  if  angular  fragments,  a  breccia;  if  the  pebbles  are  of 
quartz,  a  siliceous  conglomerate;  if  of  limestone,  a  calcareous 
conglomerate. 

3.  Shale.  —  Composed  of  clay  or  clayey  earth,  and  having 
a  shaly  structure.     The  colors  are  of  all  dull  shades  from 
gray  to  black.     When  the  shaly  structure  is  very  imperfect 
and  the  rock  is  quite  fragile,  it  is  a  marlyte. 

4.  Tufa.  —  A  kind   of  volcanic   sandstone,   composed   of 
volcanic  sand   or  pulverized  volcanic  rocks :  color,  usually 
browrlish,  brownish-yellow,  grayish,  and  reddish. 

2.   Metamorphic  Rocks. 

1.  Granite.  —  A  crystalline  rock,  consisting  of  quartz,  feld- 
spar, and  mica.     Color,  usually  light  or  dark  gray,  or  flesh- 
red,  the  latter  shade  derived  from  a  flesh-colored  feldspar. 
The  quartz,  uncleavable  and  usually  grayish-white  in  color ; 
the  feldspar,  white  to  flesh-red,  and  yielding  smooth,  shining 
surfaces  by  cleavage ;  the  mica,  white  to  black,  and  affording 
thin,  flexible  leaves  by  cleavage. 

2.  Gneiss.  —  Like  granite   in    constitution^  but  somewhat 
schistose,  owing  to  the  arrangement  of  the  minerals,  espe- 
cially the  mica,  in  planes,  and,  consequently,  having  a  banded 
appearance  on  a  surface  of  fracture  transverse  to  the  struc- 
ture.    If  the  color  of  the  gneiss  is  dark  gray,  it  is  banded 
usually  with  black  lines.     Aloag   the   micaceous  planes  it 


24  LITHOLOGICAL   GEOLOGY. 

breaks  rather  easily  into  slabs,  which  are  sometimes  used  for 
flagging. 

3.  Mica  Schist.  —  Related  to  gneiss,  but  consisting  mainly 
of  mica,  with  quartz  and  more  or  less  of  feldspar,  and,  in 
consequence  of  the  mica,  breaking  into  thin  slabs.     The  slabs 
have  a  glistening  surface.     In  regions  of  mica  schist  the  dust 
of  the  roads  is  often  full  of  shining  particles  of  mica. 

4.  Syenyte ;  *   Hornblendic    Gneiss  ;   Hornblendic    Schist.  — 
Syenyte  resembles  granite,  but  contains  hornblende  in  place  of 
mica :  the  hornblende  may  be  distinguished  from  mica  by  its 
less  perfect  cleavage,  and  by  the  brittleness  of  the  laminae 
which  cleavage,  with  some  difficulty,  affords.     A  rock  like 
gneiss,  but  containing  hornblende  in  place  of  mica,  is  called 
syenytic  gneiss.     A   black   or  greenish-black   schistose   rock 
consisting  almost  wholly  of  hornblende  is  called  hornblende 
schist.     Hyposyenyte  is  a  syenyte  without  quartz. 

5.  Hydromica  Slate.  —  A  slaty  fine-grained  micaceous  slate 
feeling  somewhat  greasy  to  the  fingers.     It  used  to  be  called 
talcose  slate ;  but  it  contains  a  hydrous  mica  instead  of  talc. 

6.  Chlorite  Slate.  —  A  slaty  rock  containing  an  olivergreen 
mineral  called  chlorite,  which  is  related   to   talc   in  being 
magnesian,  but  contains  oxide  of  iron,  and  is  hardly  greasy 
in  feel.     Color  dark  green,  and  often  olive-green. 

7.  Slate,  Clay-Slate,  or  Argillyte.  —  These  are  different  names 
of  roofing-slate  and  the  allied  slaty  rocks.     The  texture  is 
hardly  at  all  crystalline,  but  the  slates  in  the  most  perfect 
kinds   are   hard,  smooth   in   surface,  and  not  absorbent  of 
water.     Color  blue-black,   purplish,  greenish,  and   of  other 
shades. 

There  is  a  gradual  passage  of  the  above  rocks  from  granite 
into  gneiss;  froni  gneiss  into  mica  schist;  and  from  mica 
schist,  hydromica  slate,  and  chlorite  slate  into  argillyte. 

8.  Quartz   Rock ;   Quartzyte.  —  There    is    also    a    gradual 

*  In  the  names  of  rocks  the  last  syllable  is  spelt  with  a  "y"  instead  of  an 
"i,"  to  distinguish  them  from  the  names  of  minerals.  The  term  granite  is 
made  an  exception,  because  it  is  of  so  common  use  in  general  literature. 


KINDS  OF  ROCKS.  25 

passage,  through  the  more  or  less  complete  absence  of  the 
feldspar,  into  a  micaceous  quartz  rock  having  a  schistose 
structure ;  and,  by  a  more  or  less  complete  absence  of  the 
mica,  into  a  pure  massive  quartz  rock,  called  also  quartzyte. 
Quartzyte  is  only  a  very  firmly  consolidated  sandstone  made 
of  quartz  sand.  The  consolidation  has  been  produced  by 
the  aid  of  heat,  just  as  crystallization  into  gneiss  has  been 
produced.  For  the  former  the  sandstones  were  purely  sili- 
ceous, or  nearly  so,  and  for  the  latter,  earthy  sandstones. 

9.  Itacolumyte.  —  A  peculiar  laminated  quartz  rock  occurs 
in  many  gold-regions,  which  bends  without  breaking,  when 
in  large  thin  plates.  It  contains  scales  of  a  hydrous  mica, 
and  owes  to  this  its  laminated  structure,  toughness,  and 
flexibility. 

3.  Calcareous  Rocks. 

a*  Uncrystalline. 

1.  Common  Limestone.  —  A  compact  rock  of  grayish  and 
other  dull  shades  of  color  to  black.     It  breaks  with  little  or 
no  lustre,  and  with  either  a  slightly  rough  or  a  smooth  sur- 
face of  fracture.     Consists  essentially  of  carbonate  of  lime, 
though  often  very  impure  from  the  presence  of  clay  or  earth. 
When  containing  fossils,  it  is  called  fossiliferous  limestone. 
When  consisting  of  carbonate  of  lime  and  magnesia,  it  is  a 
magnesian   or   dolomitic  limestone,  or  dolomite,  a  kind  not 
distinguishable  by  the   eye   from   ordinary  limestone.     For 
the  distinctive  characters,  see  page  19.     When  impure,  and 
therefore   good  for  making   hydraulic  lime  (lime   that  will 
make  a  cement  which  sets  under  water),  it  is  called  hydraulic 
limestone. 

Many  varieties  of  common  limestone  are  polished  and  used 
as  marbles ;  they  have  black,  reddish,  yellow,  gray,  and  other 
colors.  Some  kinds  contain  fossils. 

2.  Oblyte.  —  A  limestone  consisting  of  concretions  as  small 
as  the  roe  of  fish,  or  smaller,  —  whence  the  name,  from  the 
Greek  MOV,  egg.     Oolyte  or  oolitic  limestone  occurs  in  all  the 


26  LITHOLOGICAL   GEOLOGY. 

geological  formations,  and  is  forming  in  modern  seas  about 
some  coral  reefs. 

3.  Travertine.  —  (See  page  22.)  Stalactites  are  limestone 
concretions,  of  the  form  of  icicles,  hanging  from  the  roofs  of 
caverns ;  and  Stalagmite  is  the  same  material  covering  their 
floors.  The  waters  trickling  through  limestone  rocks  hold 
some  carbonate  of  lime  in  solution  (in  the  state  of  bicarbon- 
ate) ;  and  its  deposition,  as  the  dropping  water  evaporates, 
produces  these  concretions  and  incrustations. 

to.  Crystalline. 

Granular  Limestone ;  Statuary  Marble.  —  Limestone  hav- 
ing a  crystalline  granular  texture,  and,  consequently,  glisten- 
ing on  a  surface  of  fracture.  The  pure  white  kind,  looking 
when  broken  much  like  loaf-sugar,  is,  when  of  firm  texture, 
the  marble  used  for  statuary ;  and  both  this  and  coarser 
varieties  are  employed  for  marble  buildings.  Most  of  the 
handsome  clouded  marbles  are  here  included. 

4.   Igneous  Rocks. 

1.  Granite-like  rocks.  —  Granite,  syenyte,  and  hyposyenyte 
are  here   included.     Yet  far  the   larger  part  of  granite  is 
either  of  metamorphic  origin  or  vein-formation.     Most  igne- 
ous rocks  contain  little  or  no  quartz. 

2.  Dioryte    consists   of   a  feldspar   (albite,   or    oligoclase) 
and  hornblende;  and,  though  it  may  be  light  colored  from 
the  abundance  of  the  feldspar,  it  is  usually  dark  green  and 
greenish-black,  from  the  preponderance  of  the  hornblende. 

3.  Doleryte  consists  of  the  feldspar  labradorite  with  pyrox- 
ene, and  has  greenish-black,  brownish-black,  and  black  colors. 
It  is  also  often  called  trap.     It  may  be  either  crystalline 
granular,  or  of  a  flinty  compactness.     It  contains  also  grains 
of  magnetite.     Basalt  is  only  a  compact  variety  of  doleryte. 
Didbasyte  is  a  chloritic  or  hydrous  doleryte. 

4.  Peridotyte  is  a  doleryte  containing  grains  of  a  green 
silicate,  of  a  bottle-glass  green  color,  called  chrysolyte  or  olivine. 


STRATIFIED   ROCKS.  27 

5.  Porphyry,  —  True  porphyry  consists  of  feldspar  (ortho- 
clase)  in  a  compact  condition,  with  disseminated  crystals  of 
feldspar  of  a  paler  color ;  so  that  a  polished  surface  is  covered 
with   angular  spots.     But  any  rock  containing  distinct  dis- 
seminated crystals  of  feldspar  is  said  to  be  porphyritic. 

6.  Trachyte.  —  Consists  of  feldspar,  partly  glassy,  and  has 
a  rough  surface  of  fracture.     Hornblende  is  often  present, 
and  sometimes  quartz.     Phonolyte  is  a  feldspathic  rock  of 
smoother  surface  than  trachyte,  containing  hydrous  minerals 
of  the  zeolite  family. 

7.  Lava.  —  Any  rock  that  has  flowed  in  streams  from  a 
volcano,  especially  if  it  contains  cavities,  or,  in  other  words, 
is  more  or  less  scoriaceous.     It  is  usually  a  dohryte,  perido- 
tyte,  or  trachyte  in  composition. 

8.  Scoria  is  a  light  lava,  full  of  cavities,  like  a  sponge; 
and  pumice,  a  white  or  grayish  feldspathic  scoria,  having  the 
air-cells  long  and  slender,  so  that  it  looks  as  if  it  were  fibrous. 

Igneous  rocks,  like  doleryte  and  trachyte,  sometimes  take 
in  water  when  in  process  of  eruption  (deriving  it  from  sub- 
terranean streams  or  sources),  and  then  become  hydrous. 
Thus  dolerytic  lava  is  made  into  diabasyte,  and  trachyte  into 
phonolyte. 

II. -CONDITION,  STRUCTURE,  AND  ARRANGE- 
MENT OF  ROCK-MASSES. 

The  rocks  which  have  been  described  are  the  material  of 
which  the  great  rock-masses  or  terranes  of  the  globe  consist. 
These  rock-masses  occur  under  three  conditions :  —  1.  The 
Stratified;  2.  Unstratified ;  3.  The  Vein-form. 

1.  The  Stratified  condition.  —  Stratified  rocks  are  those  which 
lie  in  beds  or  strata.  The  word  stratum  (the  singular  of 
strata)  is  from  the  Latin,  and  signifies  that  which  is  spread 
out.  The  earth's  rocky  strata  are  spread  out  in  beds  of  vast 
extent,  many  of  them  being  thousands  of  square  miles  in 
area  and  thousands  of  feet  in  thickness. 


28  LITHOLOGICAL  GEOLOGY. 

The  stratified  rocks  exposed  to  view  over  the  earth  far 
exceed  in  surface  the  unstratified.  They  are  the  rocks  of 
nearly  the  whole  of  the  United  States  and  of  almost  all 
of  North  America,  and  not  less  of  the  other  continents. 
Throughout  Central  and  Western  New  York,  and  the  States 
south  and  west,  the  rocks,  wherever  exposed,  are  seen  to  be 
made  up  of  a  series  of  beds.  And  if  the  beds  are  less  dis- 
tinct over  a  large  part  of  New  England,  it  is,  in  general,  only 
because  they  have  been  obscured  by  the  upturning  and  crys- 
tallization which  the  rocks  have  undergone  since  they  were 
formed. 

Fig.  10. 


The  preceding  figure  represents  a  section  of  the  rocks 
along  the  river  below  Niagara  Falls.  It  gives  some  idea 
of  the  alternations  which  occur  in  the  strata.  In  a  total 
height  of  250  feet  (165  feet  at  the  Falls,  at  F,  on  the  right) 
there  are  on  the  left  six  different  strata  in  view  and  parts  of 
two  others,  the  upper  and  lower,. making  eight  in  all.  Num- 
ber 1  is  gray  argillaceous  sandstone ;  2,  gray  and  red  argil- 
laceous sandstone  and  shale ;  3,  flagstone,  or  hard  laminated 
sandstone ;  4,  reddish  shale,  or  marlyte,  and  shaly  sandstone ; 
5,  shale ;  6,  limestone ;  7,  shale ;  8,  limestone.  Only  two  of 
these  strata,  7  and  8,  are  in  sight  at  the  Falls  (at  F).  The 
alternations  are  thus  numerous  and  various  in  all  regions  of 
stratified  rocks.  Along  the  canon  of  the  Colorado  there  are 
in  some  places  more  than  8,000  feet  of  stratified  beds,  show- 
ing their  edges  in  lofty  precipices,  and  in  the  mountains  tow- 
ering above  the  adjoining  plains. 

It  must  not  be  inferred  that  the  earth  is  covered  by  a 
regular  series  of  coats,  the  same  in  all  countries ;  for  this  is 
far  from  the  truth.  Many  strata  occur  in  New  York  that  are 


VEINS.  29 

not  found  in  Ohio  and  the  States  west,  and  many  in  South- 
ern New  York  that  are  not  in  Northern ;  and  each  stratum 
varies  greatly  in  different  regions,  sometimes  being  limestone 
in  one  and  sandstone  in  another. 

A  stratum  is  a  bed  of  rock  including  all  of  any  one  kind 
that  lie  together,  as  either  Nos.  1,  2,  3,  4,  5,  6,  7,  or  8  in  the 
preceding  figure. 

A  formation  includes  all  the  various  kinds  of  strata  that 
were  formed  in  one  age  or  period,  as  the  Carboniferous  forma- 
tion or  that  of  the  coal  era.  A  subdivision  of  a  formation, 
including  two  or  more  related  strata,  is  often  called  a  group. 

A  layer  is  one  of  the  subdivisions  of  a  stratum.  A  stratum 
may  consist  of  an  indefinite  number  of  layers. 

2.  TJnstratified   condition.  —  Unstratified   rocks   are   those 
which  do  not  lie  in  beds  or  strata.      Mountain-masses  of 
granite  are  often  without  any  appearance  of  stratification. 
The  rock  of  the  Palisades,  on  the  Hudson,  stands  up  with  a 
bold  columnar  front,  and  has  no  division  into  layers.     There 
are  similar  rocks  about  Lake  Superior.     Most  lavas  of  vol- 
canoes have  flowed  out  in  successive  streams ;  and,  conse- 
quently, volcanic  mountains  are  generally  stratified.     But  in 
some  volcanic  regions  the  rocks  rise  into  lofty  summits  with- 
out stratification.      Although   true  granite  bears  no  marks 
of  proper  stratification,  it  very  often  passes  insensibly  into 
gneiss,  which  is  a  stratified  rock ;  and  there  is  evidence  in 
this  fact  that  granite  is,  generally,  a  stratified  rock  which 
has  lost  the  appearance  of  stratification  in  consequence  of 
the  crystallization  it  has  undergone. 

3.  Vein-form  condition.  —  When  rocks  have  been  fractured, 
and  the  fissures  thus  made  have  been  filled  with  rock-mate- 
rial of  any  kind,  or  with  metallic  ores,  the  fillings  are  called 
veins.     Veins  are  therefore  large  or  small,  deep  or  shallow, 
single  or  like  a  complete  network,  according  to  the  char- 
acter of  the  fractures  in  which  they  were  formed.      They 
may  be  as  thin  as  paper,  or  they  may  be  many  yards,  or  even 
rods,  in  width.     Figs.  11  to  14  represent  some  of  them.     In 


30 


LITHOLOGICAL  GEOLOGY. 


Fig.  11  there  are  two  veins,  a  and  b;  in  Fig.  12,  a  network 
of  thin  veins ;  in  Fig.  13,  two  of  irregular  form,  —  a  kind  not 


Fig.  11. 


Fig.  12. 


uncommon ;  in  Fig.  14,  two  large  veins,  of  still  more  irregu 
lar  character,  crossing  one  another. 


Fig.  13. 


Fig.  14. 


Fig.  15. 


if 


Many  veins  have  a  banded  structure,  like  Fig.  15.  In  this 
vein  the  layers  1,  3,  6  consist  of  quartz;  2,  4,  of  gneis- 
soid  granite  ;  5,  of  gneiss.  Most  metallic 
veins  are  of  this  kind:  the  ores  lie  in  one 
or  more  bands  alternating  with  other  stony 
bands  consisting  of  different  minerals  or 
rock-material,  as  calcite,  quartz,  fluoryte,  etc. 
Those  veins  that  have  been  filled  with 
melted  rocks  are  usually  called  dikes;  they 
are  not  banded,  and  have  regular  walls, 
and  the  rocks  are  igneous  rocks.  They  are 
often  transversely  columnar  in  structure. 
Fig.  16  represents  a  portion  of  a  dike  hav- 
ing this  transversely  columnar  structure. 


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STRUCTURE   OF  ROCKS.  31 

4,  Relation  of   stratified   and   true   unstratified   rocks   and 
veins  in  the  earth's  crust.  —  The   relations   of  the   stratified 
and  unstratified  rocks  in  the  earth's  crust  will 
be   understood   after   considering   the   origin  of 
the  crust. 

The  crust  is  believed  to  be  the  cooled  exterior 
of  a  melted  globe.  After  the  first  crusting  over 
of  the  surface  of  the  sphere,  the  ocean  commenced 
at  once  to  make  stratified  rocks  over  the  exterior 
through  the  wear  of  the  crust-rocks,  and  the  strat- 
ifying of  the  sand  or  mud  thus  made;  while  the  continued 
cooling,  going  on  very  slowly,  made  unstratified  rocks  beneath 
this  first  crust  as  its  inner  portion.  The  ocean  thus  worked 
over  and  covered  up  with  strata  nearly  all,  if  not  all,  the 
original  unstratified  crystalline  rocks.  Hence,  true  unstrati- 
fied rocks  —  that  is,  those  which  were  unstratified  in  their 
first  formation  —  are  of  very  small  extent  over  the  globe. 
As  mentioned  on  page  26,  even  ordinary  granite  is  not 
generally  of  this  kind.  Veins  are  a  result  of  fractures  of  the 
crust ;  and  they  too  are  of  very  limited  distribution. 

Geology,  consequently,  has  for  its  study,  chiefly,  strati- 
fied rocks.  Nearly  all  the  facts  in  geological  history  are 
derived  from  rocks  of  this  kind.  It  is,  therefore,  important 
that  the  various  details  with  regard  to  their  structure  and 
arrangement  should  be  well  understood  by  the  student. 

Stratified  Condition. 
I .  Structure. 

1.  Massive,  laminated,  and  shaly  structures,  —  The  massive, 
laminated,  and  shaly  structures  of  layers  have  been  explained 
on  page  22.  The  massive  is  represented  in  Fig.  17  a;  the 
laminated,  in  Fig.  17  ~b ;  and  the  shaly,  in  Fig.  17  c.  Sand- 
stone is  more  or  less  laminated,  according  to  the  proportion  of 
clay  or  fine  earthy  material  it  contains.  The  same  is  true 
of  limestone. 


32 


LITHOLOGICAL   GEOLOGY. 


2.  Beach  structure.  —  The  structure  of  the  upper  part  of  a 
beach  is  illustrated  in  Fig.  17  d.  Instead  of  being  composed 
of  evenly  laid  material,  it  consists  of  many  irregular  small 
layers  as  deposited  or  thrown  together  by  the  waves  during 
storms.  The  lower  part  of  the  beach  has  an  even  slope  of 
usually  5  to  8  degrees,  and  the  sands  beneath  are  in  beds 
having  the  same  slope. 

Fig.  17. 


3.  Ebb-and-flow  structure.  —  Having  portions  of  the  beds 
obliquely  laminated  (as  shown  in  Fig.  17  e)  while  other  alter- 
nate layers  are  often  laminated  horizontally.     Such  a  struc- 
ture is  formed  where  currents  intermit  at  intervals  or  are 
reversed,  as  in  the  ebb  and  flow  of  the  tides. 

4.  Flow-and-plunge  structure.  —  Where  the  waves  plunge 
heavily  in  connection  with  a  flow  of  tidal  or  other  currents, 
the  obliquely  laminated  layer  is  broken  up  into  wave-like 
or  wedge-shaped   parts,   as   illustrated   in   Fig.  17  g.     This 
structure  is  common  in  stratified  drift. 

5.  Wind-drift  structure.  —  Having  the   subordinate  layers 
dipping  in  various  directions,  sometimes  curving  and  some- 
times straight,  as  shown  in  Fig.  17  /.     The  hills  of  sand 
formed  by  the  winds  on  a  sea-coast  are  usually  thus  strati- 


STRUCTURE   OF  ROCKS. 


33 


fied.  The  sands  drifted  over  the  rising  heaps  form  layers 
conforming  to  the  outer  surface,  and  so  may  slope  at  all 
angles.  In  storms  the  heaps  may  be  blown  away  in  part, 
and  afterward  be  completed  again ;  but  then  the  layers  will 
conform  to  the  new  outer  surface,  and  hence  have  a  different 
direction.  In  this  way,  by  successive  destructions  and  re- 
completions,  a  bed  of  sand  may  be  made  which  shall  consist 
of  parts  sloping  in  one  direction  and  other  parts  in  directions 
very  different,  with  numerous  abrupt  transitions,  as  illus- 


trated in  the  figure. 


Fig.  18. 


Pig.  19. 


6.  Ripple-marks.  —  A  gentle  flow  of  water,  or  its  vibration, 
over  mud  or  sand  ripples  the  surface.     Sandstone  and  clayey 
rocks  are  often  covered  with  such  ripple-marks  (Fig.  18). 

7.  Rill-marks.  —  When  the  waters  of  a  spreading  or  return- 
ing wave  on  a  beach  pass  by  shells  or  stones  lodged  in  the 
sand,  the  rills  furrow  out  little  channels.     Fig.  19  shows  such 
rill-marks  alongside  of  shells  in  a  Silurian  sandstone. 

8.  Mud-cracks.  —  When  a  mud-flat  is  exposed  to  the  air 
or  sun  to  dry,  it  becomes  cracked  to  a  few  inches  or  feet  in 
depth.     Fig.    20   represents   mud-cracks   in   an   argillaceous 
sandstone.     The  cracks  were  subsequently  filled  with  stony 

2*  c 


34 


LITHOLOGICAL   GEOLOGY. 


material,  which  became  harder  even  than  the  rock  itself;  so 
that  the  filling  stands  prominent  above  a  weathered  surface 
of  the  rock  :  it  is  actually  a  network  of  veins. 


Tig.  20. 


Fig.  21. 


Fig.  22. 


9.  Rain-prints.  —  The  impressions  of  rain-drops  on  sand, 
or  a  half-dry  mud,  have  often  been  preserved  in  the  rocks, 
appearing  as  in  Fig.  21. 

10.  Concretionary  structure.  —  Layers  often  contain  spheres 
or  disks  of  rock,  which  are  called  concretions.     They  result 
from  a  tendency  in  matter  to  concrete  or  solidify  around 

centres.  Some  are  no  larger  than  grains  of 
sand  or  the  roe  of  fish,  as  in  oolitic  limestone 
(page  25).  Others  are  as  large  as  peas  or  bul- 
lets, and  others  a  foot  or  more  in  diameter. 
The  granite  of  the  mountains  about  the  Yo- 
semite,  in  California,  has  rounded  forms  above 
owing  to  a  concretionary  structure  thousands 

of  feet  in  radius. 

Fig.  22  represents  a  spherical  concretion ;  Fig.  23,  a  rock 

made  up  of  rounded  concretions,  showing  also  that  there  is 

sometimes  a  concentric  structure ;  Fig.  24,  one  with  flattened 

concretions. 

Concretions,  are  usually  globular  in  sandstones,  lenticular 


STRUCTURE   OF  ROCKS. 


35 


in  laminated  sandstones,  and  flattened  disks  in  argillaceous 
rocks  or  shales.     All  these  kinds  are  shown  in  Fig.  25.     The 


Fig.  23. 


Fig.  24. 


Fig.  25. 


balls  are  sometimes  hollow,  and  the  disks  mere  rings.     Fre- 
quently the  concretions  have  a  shell  or  other  organic  object 


Fig.  26. 


Fig.  27. 


Fig.  28. 


at  centre  (Fig.  26).  They  are  often  cracked  through  the 
interior  (Fig.  27),  the  outside  in  such  a  case  having  solidified 
while  the  inside  was  still  moist,  and  the  latter  afterward 
cracking  as  it  dried :  in  such  a  case  the  cracks  may  become 
filled  with  other  minerals,  so  that  the  concretion,  on  being 
sawn  in  two  and  polished,  may  have  great  beauty,  owing 
to  the  crystals  (Fig.  28),  as  of  quartz,  or  the  layers,  as  of 
agate,  which  they  contain.  Such  a  cavity  lined  with  crystals 
is  called  a  geode.  Sometimes  they  contain  a  loose  ball  with^- 
in,  —  a  concretion  within  a  concretion. 

Basaltic  columns  (Fig.  29)  are  columns  of  igneous  rock. 
As  the  rock  cools  it  contracts,  and  hence  it  often  becomes  di- 
vided into  prisms  at  right  angles  to  the  cooling  surfaces.  In 
the  consolidation  there  is  a  tendency  to  the  concretionary 
structure,  as  often  shown  by  the  tops  of  the  columns  being 
concave,  or  their  becoming  so  when  the  rock  decomposes. 

11.  Jointed  structure.  —  The  rocks  of  a  region  are  often  di- 
vided very  regularly  by  numerous  straight  planes  of  fracture, 


36 


LITHOLOGICAL   GEOLOGY. 


Fig.  29. 


all  parallel  to  one  another,  and  cutting  through  to  great  depths. 
Such  deep  planes  of  fracture  may  characterize  the  rocks  over 
areas  hundreds  of  miles  in  ex- 
tent. They  are  called  joints; 
and  a  rock  thus  divided  is  said  to 
present  a  jointed  structure.  In 
many  cases  there  are  two  sys- 
tems of  joints  in  the  same  region, 
crossing  one  another,  so  that  they 
divide  the  rock  into  angular 
blocks,  or  give  to  a  "bluff  a  front 
like  that  of  a  fortification  or  a  broken  wall,  as  shown  in  Fig. 
30,  —  a  view  from  the  shores  of  Cayuga  Lake.  The  direc- 
tions of  such  joints  are  facts  which  the  geologist  notes  down 
with  care.  The  divisional  planes  in  Fig.  29  also  are  called 
joints. 

Fig.  30. 


12.  Slaty  cleavage.  —  The  term  slaty  has  been  explained 
on  page  22.  But  one  important  fact  regarding  the  structure 
is  not  there  stated,  which  is,  that  the  slates  are  usually  trans- 
verse to  the  bedding,  that  is,  they  often  cross  the  layers  of 
stratification  more  or  less  obliquely,  instead  of  conforming 
to  the  layers  like  the  slialy  structure.  Slaty  cleavage  is  in 
this  respect  like  the  jointed  structure ;  but  it  differs  in 
having  the  planes  of  fracture  or  divisional  planes  so  numer- 
ous that  the  rock  divides  into  slates  instead  of  blocks. 

Slaty  cleavage  is  confined  to  fine-grained  argillaceous 
rocks.  If  a  rock  is  a  coarse  argillaceous  rock  or  an  argilla- 


POSITIONS  OF  STRATA.  37 

ceous  sandstone,  it  may  have  a  jointed  structure,  but  will 
not  have  the  true  slaty  cleavage.  In  Fig.  31  the  lines  of 
bedding  or  stratification  are  shown  at  a,  b,  c,  d,  while  the 


Fig.  32. 


transverse  lines  correspond  to  the  direction  of  the  slates. 
The  same  is  shown  in  Fig.  32,  with  the  addition  of  a  slight 
irregularity  in  the  slates  along  the  junction  of  two  layers. 

2.  Positions  of  Strata. 

1.  Original  position  of  strata.  —  Horizontal  position.  —  Ordi- 
nary stratified  rocks  were  once  beds  of  sand  or  earth,  or  of 
other  rock-material,  spread  out  by  the  currents  and  waves  of 
the  ocean,  or  the  waters  of  lakes  or  rivers,  or  by  the  winds. 

When  the  larger  portion  of  the  beds  over  the  North  Amer- 
ican continent  were  formed,  the  continent  lay  to  a  great 
extent  beneath  the  ocean,  as  the  bottom  of  a  great,  though 
mostly  shallow,  continental  sea.  The  principal  mountain - 
chains  —  the  Eocky  Mountains  and  the  Appalachians  —  had 
not  yet  been  made,  and  the  surface  of  the  submerged  land 
was  nearly  flat.  The  fact  that  those  beds  were  really  marine 
is  proved  by  their  containing,  in  most  cases,  marine  shells, 
crinoids,  or  corals,  the  relics  of  marine  life;  and  the  great 
extent  of  the  continental  seas  is  indicated  by  the  fact  that 
the  beds  cover  surfaces  tens  of  thousands  of  square  miles  in 
area,  some  of  them  reaching  from  the  Atlantic  border  west- 
ward beyond  the  Mississippi.  In  such  great  continental 
seas,  having  the  bottom  nearly  flat,  the  deposits  made  by 
means  of  the  currents  and  waves  would  have  been  nearly 
or  quite  horizontal.  As  they  increased,  they  would  near  the 
surface ;  and  here  the  action  of  the  waves  would  level  off 


38 


LITHOLOGICAL   GEOLOGY. 


the  upper  surface  of  the  beds,  whether  accumulations  of  sand 
or  earth,  or  of  shells  or  corals.  If  the  bottom  over  the  region 
were  very  slowly  sinking,  the  accumulations  might  go  on 
thickening,  and  the  beds  continue  to  have  the  same  level 
or  horizontal  position. 

Many  strata  have  been  formed  along  the  borders  of  the 
continents ;  and  here,  also,  they  take  horizontal  positions. 
The  bottom  of  the  border  of  the  Atlantic,  south  of  Long 
Island,  is,  for  eighty  miles  from  the  coast-line,  so  nearly 
horizontal  that  it  deepens  only  1  foot  for  every  600  to  700 
feet;  and  if  the  area  were  above  the  ocean,  no  eye  would 
detect  that  it  was  not  perfectly  level.  It  is  obvious  that 
deposits  over  such  a  continental  border  wrould  be  very  nearly 
horizontal. 

The  deltas  about  the  mouths  of  great  rivers,  like  that  of 
the  Mississippi,  cover  sometimes  thousands  of  square  miles. 
They  are  made  of  the  sands  and  earth  brought  down  by  the 
river  and  spread  out  by  the  currents  of  the  river  and  ocean. 
They  are,  therefore,  examples  of  the  deposition  of  rock-mate- 
rial on  a  scale  of  great  extent ;  and  various  strata  have  been 
formed  as  deltas  are  formed.  The  beds  of  delta-deposits  are 
always  hoi*izontal  or  nearly  so. 

Other  beds  were  originally  vast  marshes,  like  the  marshes 
of  the  present  day,  only  larger.  Such  was  the  condition  of 
those  beds  in  the  coal-formation  that 
contain  coal.  Marshes  have  a  horizon- 
tal surface ;  and  marsh  deposits,  as  they 
accumulate,  have  a  horizontal  structure. 
Many  coal-beds  contain  stumps  of  trees 
rising  out  of  the  coal  (Fig.  33) ;  and  they 
always  stand  vertically  on  the  bed,  how- 
ever much  the  latter  may  be  displaced,  showing  that  the  bed 
was  horizontal  when  it  was  formed,  or  when  the  trees  were 
growing. 

Exceptions  to  a  horizontal  position.  —  When  a  river  empties 
into  a  lake  or  sea,  the  bottom  of  which,  near  its  mouth,  is 


Fig.  33. 


DISLOCATIONS   OF   STRATA.  39 

more  or  less  inclined,  the  deposits  of  detritus  made  by  the 
river  will  for  a  while  conform  to  the  slope  of  the  bottom, 
as  in  Fig.  34.  When  rivers  fall  down  precipices,  they  make 
a  steep  bank  of  earth  at  the  foot,  whose  layers,  if  any  are 

Fig.  34. 


observable,  take  the  slope  of  the  bank.  The  sand-accumula- 
tions of  a  sloping  beach  have  the  slope  of  the  beach  (page 
32),  or  usually  a  dip  of  5°  to  8°. 

But  these  and  similar  cases  of  exceptions  to  a  horizontal 
position  are  of  small  extent. 

2.  Dislocations  of  strata.  —  Most  of  the  strata  of  the  globe 
have  lost  their  original  horizontal  position,  and  are  more  or 
less  inclined  ;  some  are  even  vertical. 

They  are  occasionally  bent  or  folded  as  a  quire  of  paper 
might  be  folded,  only  the  folds  are  miles,  or  scores  of  miles, 
in  sweep. 

They  have  often  also  been  fractured,  and  the  separated 
parts  have  been  pushed,  or  else  have  fallen,  out  of  their 
former  connections,  so  that  the  portion  of  a  stratum  on  one 
side  of  a  fracture  may  be  raised  inches,  feet,  or  even 
miles,  above  that  on  the  other  side. 

It  is  stated  on  page  1,  that  a  thickness  of  rock  equal  to  18 
or  20  miles  is  open  to  the  geological  explorer.  This  could 
not  be  true,  were  all  strata  in  their  original  horizontal  posi- 
tion ;  for  the  most  that  would  in  that  case  be  within  reach 
would  not  exceed  the  height  of  the  highest  mountain.  But 
the  upturning  which  the  earth's  crust  has  undergone  has 
brought  the  edges  of  strata  to  the  surface,  and  there  is  hence 
no  such  limit:  however  deep  stratified  beds  may  extend, 
there  is  no  reason  why  the  whole  should  not  be  brought  up 
so  as  to  be  exposed  to  view  in  some  parts  of  the  earth's 
surface. 


40 


LITHOLOGICAL   GEOLOGY. 


The  following  are  explanations  of  the  terms  used  in  de- 
scribing the  positions  of  strata  :  — 

7.  Outcrop.  —  The  portions  or  ledges  of  strata  projecting 
out  of  the  ground,  or  in  view  at  the  surface  (Fig.  35). 

2f  Dip.  —  The  angle  of  slope  of  inclined  or  tilted  strata. 
In  Figs.  35,  36,  d  p  is  the  direction  of  the  dip.  Both  the 
angle  of  slope  and  the  direction  are  noted  by  the  geologist : 

Fig.  35. 


thus,  it  may  be  said  of  beds,  the  dip  is  50°  to  the  south,  or 
45°  to  the  northwest,  etc. 

When  only  the  edges  of  layers  are  exposed  to  view,  it  is 
not  safe  to  take  the  slope  of  the  edges  as  the  slope  of  the 
layers;  for  in  Fig.  36  the  edges  on  the  faces  1,  2,  3,  4  are 


all  edges   of  the   same  beds,  and  only  those  of  the  face  1 
would  give  the  right  dip. 

The  dip  is  measured  by  means  of  instruments  called  clino- 
meters. In  Fig.  37,  a  I  c  d  represents  a  square  block  of 
wood,  having  a  graduated  arc  b  c  and  a  plummet  hung 
below  a.  Placed  on  the  sloping  surface  A  B,  the  position 
of  the  plummet  gives  the  angle  of  dip.  This  kind  of 
clinometer  is  often  made  in  the  form  of  a  watch  and  com- 


DISLOCATIONS   OF  STRATA. 


41 


bined  with  a  compass.  It  is  most  convenient  for  use  when  it 
has  a  square  base.  In  the  same  figure,  e  d  f  represents  another 
clinometer.  It  has  a  level  on  the  arm  d  e;  and  when  the 
arm  d  f  is  placed  on  the  sloping  surface,  the  other  arm  is 


Fig.  38. 


raised  until,  as  shown  by  this  level,  it  is  horizontal ;  the  dip 
is  the  angle  between  the  two  arms,  as  measured  on  the  arc  at 
the  joint.  To  avoid  errors  from  the  unevenness  of  a  rock,  a 
board  should  be  laid  down  first,  and  the  measurement  be 
made  on  its  surface.  When  the  instrument  has  a  square 
base  it  is  often  best  to  measure  the  dip  by  holding  it  between 
the  eye  and  the  rock,  with  one  edge  of  the  base  in  the  direc- 
tion of  the  dipping  layers. 

3.  Strike.  —  The  horizontal  direction  at  right  angles  with 
the  dip,  as  s  t  in  Fig.  35.    The  di- 
rection of  the  edges  of  layers  on  a 

surface  that  is  quite  horizontal  is 
the  true  strike. 

4.  Fault.  —  When   strata   have 
been  fractured  and  the  parts  are 
displaced,  as  in  Fig.  38,  the  dis- 
placement along   the   fracture  is 

called  a  fault.  The  coal-beds  1  and  2  in  this  figure  are 
thus  faulted  in  two  places ;  and  the  amount  of  the  fault  in 
either  is  the  number  of  feet  or  inches  that  one  part  is  above 
or  below  the  other.  The  downward  movement  of  the  middle 
portion  has  caused  a  bending  of  the  layers  in  contact  along 
one  of  the  fractures. 


42 


L1THOLOGICAL   GEOLOGY. 


5.  Folds  or  flexures.  —  The  rising  or  sinking  of  strata  in 
curving  planes,   as   represented   in   the    following    sections, 


Fig.  39. 


a'\    A 


B    at 


Fig.  39,  A,  B ;  and  in  the  natural  section,  Fig.  40,  from  the 
Appalachian  Mountains  in  Virginia. 

Fig.  40. 


S.E. 


In  Fig.  39,  a  x  is  the  axis  or  axial  plane  of  the  fold. 

6.  Anticlinal.  —  Having   the   strata   sloping  away  from   a 
common  plane  in  opposite  directions,  as  the  layers  either  side 
of  a  x  in  Fig.  39,  A  :  the  axis  is  here  called  an  anticlinal  axis ; 
and  a  ridge  made  up  of  such  strata  is  an  anticlinal  ridge. 
The  word  anticlinal  is  from  the  Greek  dvri,  in  opposite  direc- 
tions, and  K:\lva),  I  incline. 

7.  Synclinal.  —  Having  the   strata   sloping  toward  a  com- 
mon plane  from  opposite  directions.     In  Fig.  39,  B,  a  a?,  a  x 
are  anticlinal  axes,  and  a'  x',  between  the  others,  a  synclinal 
axis;  or,  viewing  the  former  as  anticlinal  ridges,  the  latter 
is  a  synclinal  valley.     The  word  synclinal  is  from  the  Greek 
<rvv,  together,  and  K\iv<o,  I  incline. 

8.  Monoclinai  —  Having   the   strata   sloping   in   only   one 
direction.     A  valley  made  by  the  fracture  of  strata  and  the 
slide  of  one  side  past  the  other,  the  dip  of  the  two  portions 
remaining  unaltered  or  but  little  changed,  is  called  a  monocli- 
nal  valley.    The  word  monodinal  is  from  the  Greek  fioW?,  one, 
and  K\wo). 

9.  Geanticllnal,  Geosynclinat.     Bendings  of  the  earth's  crust, 
geanticlinal  an  upward  bending,  and  geosynclinal  a  downward 
bending.     These  words  are  from  the  Greek  for  earth  and  the 
word  anticlinal  or  synclinal. 


UNCONFORMABLE   STRATA. 


43 


Fig.  41. 


Pig.  42. 


121    3'2'  1 


10.  Denudation ;  Decapitated  Folds.  —  If  the  top  of  the  fold 
in  Fig.  41  were  cut  off  at  a  b,  there  would  remain  the 
part  represented  in  Fig.  42,  in 
which  there  is  no  appearance 
of  any  fold,  and  only  a  uniform 
series  of  dips;  and  although  1', 
2',  3'  appear  to  be  the  lower  stra- 
ta of  the  series,  they  are  ac- 
tually parts  of  1,  2,  3.  A  long 

series  of  such  folds  pressed  together,  and  then  decapitated, 
would  make  a  series  of  uniform  dips  over  a  wide  extent  of 
country. 

The  wear  of  the  ridges  of  a  country  by  water  has  often 
produced  the  effect  here  described  over  regions  of  folded 
rocks. 

In  other  cases,  a  similar  wear  has  removed  the  rocks  over 
great  areas,  or  filled  up  intermediate  depressions  by  soil :  so 

Pig.  43. 


that  the  rocks  are  visible  only  at  long  intervals  (as  in  Fig. 
43),  and  the  faults  which  may  exist  are  concealed  from  view. 
Many  of  the  difficulties  connected  with  the  study  of  rocks 
arise  from  this  cause. 

Pig.  44. 


77.  Unconformable  strata.  —  When  strata  have  been  tilted, 
or  folded,  and,  subsequently,  horizontal  beds  have  been  laid 
down  over  them,  the  two  sets  are  said  to  be  uncomformable, 
because  they  do  not  conform  in  dip.  It  is  a  case  of  uncon- 
formability  in  the  stratification.  Thus,  in  Fig.  44  the  beds 


44  LITHOLOGICAL  GEOLOGY. 

a  b  are  unconformable  to  those  below  them ;  so  also  the  tilted 
beds  c  d  are  unconformable  to  those  beneath,  and  the  beds 
e  f  to  the  beds  c  d. 

It  is  plain  that  the  folded  rocks  represented  in  Fig.  44 
are  the  oldest,  and  that  they  were  folded  before  a  I  or  c  d 
were  deposited.  Again,  it  is  evident  that  the  beds  c  d  are 
older  than  the  beds  e  /,  and  also  that  they  were  tilted  and 
faulted  before  the  beds  6 /were  formed.  Thus  the  geologist 
arrives  at  the  relative  periods  of  occurrences  in  geological 
time.  If  the  precise  age  of  the  three  sets  of  rocks  here 
represented  could  in  any  case  be  ascertained  (as  they  gener- 
ally may  be),  the  periods  of  uplift  would  be  more  precisely 
determined. 

3.  Order  of  Arrangement  of  Strata. 

It  has  been  explained  that  the  strata  are  historical  records 
of  past  conditions  of  the  earth's  surface.  In  order,  therefore, 
that  the  records  should  make  an  intelligible  history,  there 
must  be  some  way  of  arranging  them  in  their  proper  order, 
that  is,  the  order  of  time.  The  determination  of  this  wder  is 
one  of  the  first  things  before  the  geologist  in  his  examina- 
tions of  a  country. 

Many  difficulties  are  encountered. 

1.  The  strata  of  the  same  period  or  time  —  called  equiva- 
lent strata,  because  approximately  equivalent  in  age  —  differ, 
even  on  the  same  continent.     Sandstones  and  shales  were 
often  forming  along  the  Appalachians  in  Pennsylvania  and 
Virginia,  when  limestones  were  in  progress  over  the  Missis- 
sippi Valley.     The  chalk-formation  in  England  contains  thick 
strata  of  chalk ;  but  in  Eastern  North  America  the  same  for- 
mation exists  without  any  chalk. 

2.  When  rocks  have  been  forming  in  one  region,  there 
have  been  none  in  progress  in  many  others.     Hence  the  series 
of  strata  serving  as  records  of  geological  events  is  nowhere 
perfect.     In  one  country  one  part  will  be  very  complete ;  in 
another,  another  part ;  and  all  have  their  long  blanks,  —  that 


EQUIVALENCY   OF   ROCKS.  45 

is,  large  parts  of  the  series  entirely  wanting.  In  New  York 
and  the  States  west  to  the  Mississippi,  there  is  only  part  of 
the  lower  half  of  the  series.  In  New  Jersey  there  is  part  of 
the  lower  half  and  part  of  the  upper  half,  with  wide  breaks 
between.  Over  a  large  part  of  Northern  New  York  there 
exist  only  the  very  earliest  of  rocks. 

The  thickness  of  the  fossiliferous  series  in  the  State  of 
New  York,  south  of  its  centre,  is  about  13,000  feet,  and 
north  of  its  centre  they  thin  out  to  a  few  feet ;  in  Pennsylva- 
nia, the  maximum  thickness  is  over  40,000  feet ;  in  Indiana 
and  other  adjoining  States  west  and  south,  3,500  to  6,000 
feet.  In  Great  Britain,  the  whole  thickness  above  the  unfos- 
siliferous  bottom-rocks  is  about  100,000  feet.  The  thick- 
ness here  given  is  the  sum  of  the  greatest  thickness  of  each 
of  the  successive  strata,  and  exceeds  that  existing  at  any  one 
point,  as  one  formation  may  be  thickest  in  one  district,  and 
another  in  a  district  more  or  less  remote. 

3.  The  rocks  of  a  country  are  to  a  great  extent  covered 
with  earth  or  soil,  so  that   they  can   be   examined  only  at 
distant  points. 

4.  The    strata,   in    many   regions,   have    been    displaced, 
folded,  fractured,  faulted,  and  even  crystallized  extensively, 
adding  greatly  to  the  difficulties  in  the  way  of  the  geological 
explorer. 

The  following  are  the  methods  to  be  used  in  determining 
the  true  order  of  arrangement :  — 

A.  In  sections  of  the  rocks  exposed  to  view  in  the  sides 
of  valleys   or  ridges,  the   order  should  be  directly  studied, 
and  each  stratum  traced,  as  far  as  possible,  through  all  the 
exposed  sections. 

When,  through  large  intervals,  a  covering  of  soil  or  water 
prevents  the  tracing  of  the  beds,  other  means  must  be  used. 

B.  The  aspect  or  composition   of  the   rock   may  help  to 
determine   which   strata   are   identical.      But    this    method 
should  be  used  with  caution,  for  the  reason  stated  above,  in 
§  1,  — that  rocks  made  at  the  very  same  time  may  be  widely 


46  LTTHOLOaiCAL   GEOLOGY. 

different;  and,  conversely,  those  made  in  very  different 
periods  may  look  precisely  alike  in  color  and  texture. 

C.  Fossils  afford  the  best  means  of  determining  identity. 
This  is  so  because  of  the  fact,  already  mentioned,  that  the 
fossils  of  an  epoch  are  very  similar  in  genera  —  if  not  also 
in  species  —  the  world  over ;  and  those  of  different  epochs 
are  different. 

As  the  kinds  of  fossils  belonging  to  each  period  and  age 
are  now  pretty  well  known,  and  catalogues  and  figures  have 
been  published,  the  usual  course,  on  commencing  the  in- 
vestigation of  a  stratum,  is  to  collect  its  fossils,  study  them 
with  care,  and  then  compare  them  with  the  figures  and 
descriptions  to  be  found  in  works  on  the  subject.  In  this 
way  it  has  been  proved  that  the  chalk-formation  exists  in 
Eastern  North  America,  although  there  is  no  chalk  to  be 
found  there.  In  the  same  manner,  the  equivalents  in 
America  of  the  rocks  of  Britain  and  Europe,  Asia,  and  even 
Australia,  are  ascertained ;  for  this  means  of  determination 
is  a  universal  one,  applying  to  the  equivalency  of  rocks  in 
different  hemispheres  as  well  as  those  on  the  same  continent. 

This  method  has  its  doubts  arising  from  the  fact  that  one 
continent  may  have  received  part  of  its  species  from  another 
long  after  their  first  appearance  on  that  other;  and,  from 
another  fact,  that  the  exterminations  of  species  which  have 
taken  place  at  the  close  of  a  period  may  have  been  far  more 
complete  in  one  region  than  another,  so  that  certain  species 
were  living  long  in  one  after  their  disappearance  from  the 
other.  Still,  by  proceeding  with  care  and  judgment,  and  using, 
not  isolated  facts,  but  the  whole  range  afforded  by  the  fossils, 
the  results  may  be  trusted. 


ANIMAL   AND   VEGETABLE   KINGDOMS.  47 


REVIEW    OP    THE    ANIMAL    AND    VEGETABLE 
KINGDOMS. 

THE  following  pages  on  the  Animal  and  Vegetable  King- 
doms are  inserted  in  this  place  to  prepare  the  student 
for  the  following  portion  of  the  work,  on  Historical  Geology, 
in  which  the  progress  of  life  is  a  prominent  part. 

Distinctions  bet-ween  an  Animal  and  a  Plant. 

1.  An  Animal  —  An  animal  is  a  living  being,  sustained  by 
nutriment  taken  into  an  internal  cavity  or  stomach,  through 
an  opening  called  the  mouth.     It  is  capable  of  perceiving  the 
existence  of  other  objects,  through  one  or  more  senses.     It 
has  (except  in  some  of  the  lowest  species)  a  head,  which  is 
the  chief  seat  of  the  power  of  voluntary  motion,  and  which 
contains   the   mouth.      It   is   fundamentally   a  fore-and-aft 
structure,  the  head  being  the  anterior  extremity,  and  it  is 
typically  forward-moving.     With  its  growth  from  the  germ, 
there  is  an  increase  in  mechanical  power  until  the  adult  size 
is  reached.     In  the  processes  of  respiration  and  growth,  it 
gives  out  carbonic  acid  and  uses  oxygen. 

2.  A  Plant.  —  A  plant  is  a  living  being  sustained  by  nutri- 
ment taken  up  externally  by  leaves  and  roots.     It  is  inca- 
pable of  perception,  having  no  senses.     It  has  no  head,  no 
power  of  voluntary  motion,  no  mouth.     It  is  fundamentally 
an  up-and-down  structure,  and,  with  few  exceptions,  fixed. 
In  its  growth  from  the  germ  or  seed,  there  is  no  increasing 
mechanical  power.     In  the  process  of  growth,  it  gives  out 
oxygen  and  uses  carbonic  acid. 


48  ANIMAL   KINGDOM. 

I.    Animal  Kingdom. 
I.    The  Animal  Structure. 

The  nature  of  an  animal  requires,  for  a  full  exhibition  of 
its  powers,  the  following  parts  :  — 

1.  A  stomach  and  its  appendages  to  turn  the  food  into 
blood,  with  an  arrangement  for  carrying  off  refuse  material. 

2.  A  system  of  vessels  for  carrying  this  blood  throughout 
the  body,  so  as  to  promote  growth  and  a  renewal  of  the 
structure. 

3.  A  heart,  or  forcing-pump,  to  send  the  blood  through  the 
vessels. 

4.  A  means  of  respiration,  or  of  taking  air  into  the  system 
(as  by  lungs  or  gills),  because  this  growth  and  renewal  re- 
quire the  oxygen  of  the  air  to  act  in  conjunction  with  the 
blood,  as  much  as  a  fire  requires  air  in  order  that  the  fuel 
may  burn. 

5.  Muscles,  or  contractile  fibres,  to  act  by  contraction  and 
relaxation  in  putting  the  parts  or  members  in  motion. 

6.  A  brain,  or  head-mass  of  nervous  matter,  and  a  system 
of  nerves,  branching  through  the  body,  to  serve  as  a  seat 
for  the  will  and  for  the  power  of  sensation  and  motion,  and 
to   convey  the   determinations    of    the   will   and   sensation 
through  the  body. 

In  the  lowest  form  of  animal  life,  as  some  microscopic 
Protozoans,  the  stomach  is  not  a  permanent  cavity,  but  is 
formed  in  the  mass  of  the  tissue  whenever  a  particle  of  food 
comes  in  contact  with  the  body.  In  other  words,  a  stomach 
is  extemporized  as  it  is  needed.  In  species  of  a  little  higher 
grade,  as  Polyps,  there  is  a  mouth  and  stomach,  with  mus- 
cles, an  imperfect  system  of  nerves  when  any,  and  a  means 
of  respiration  through  the  general  surface  of  the  body;  but 
there  is  no  distinct  heart,  and  the  animal  is  ordinarily  fixed 
to  a  support. 


ANIMAL  KINGDOM.  49 


2.    Subdivisions  of  the  Animal   Kingdom. 

There  are  five  distinct  plans  of  structure  according  to  which 
animals  are  made ;  and  the  species  corresponding  to  each 
make  up  what  is  called  a  sub-kingdom  in  the  kingdom  of 
animals ;  these  five  sub-kingdoms  are  the  following :  — 

1.  The  Vertebrate:  having  (as  in  Man,  Quadrupeds,  Birds, 
Eeptiles,  and  Fishes)  an  internal  jointed  skeleton,  of  which 
the  backbone  is  called  the  vertebral  column,  and  each  of  its 
joints  a  vertebra ;  and  a  bone-sheathed  cavity  along  the  back 
for  the  great  nervous  cord. 

The  remaining  sub-kingdoms  have  no  vertebral  skeleton. 

2.  The  Articulate :   having   (as   in   Insects,   Spiders,   Crabs, 
Lobsters,  Worms)  the  body  and  its  appendages  (as  the  legs, 
etc.)  articulated,  that  is,  made  up  of  a  series  of  joints. 

3.  The  Molluscan:  having  (as  in  the  Oyster,  Clam,  Snail, 
Cuttle-fish)  a  soft,  fleshy  body  without  articulations  or  joints, 
and  without  a  radiated  structure ;  and  the  appendages,  when 
any  exist,  also  without  joints.     The  name  is  from  the  Latin 
mollis,  soft. 

4.  The  Radiate:  having  (as   in  the   Polyp,   Medusa,   Sea- 
urchin,  Star-fish)  the  body,  both  externally  and  internally, 
radiate  in  arrangement,  .that  is,  having  similar  parts  or  organs 
repeated  around  a  vertical  axis,  —  as  in  a  flower  the  parts  are 
radiately  arranged  about  its  centre  or  central  axis. 

Eadiate  animals  take  after  the  vegetable  kingdom  in  type 
of  structure  (plants  also  being  radiates) ;  yet  they  are  strictly 
animals,  as  they  have  a  mouth,  stomach,  and  other  animal 
organs.  The  type  of  structure  in  each  of  the  other  sub- 
kingdoms  is  purely  animal. 

5.  The  Protozoan.  —  Besides  the  above,  there  are  other  spe- 
cies of  so  extreme  simplicity  that  neither  of  the  systems  of 
structure  above  mentioned  is  apparent  in  them,  and  these  are, 
therefore,  in  a  sense  systemless  animals.     Many  have  not  even 
a  mouth.    They  include  the  Sponges,  and  also  a  large  number 
of  minute  species,  visible  only  with  the  aid  of  a  microscope. 


50  ANIMAL   KINGDOM. 

1.    Sub-kingdom  of  Vertebrates. 

Class  1.  —  Mammals.  —  Warm-blooded  animals  that  suckle 
their  young,  as  Man,  Quadrupeds,  Whales.  Nearly  all  are 
viviparous;  a  few  (as  the  Opossum  and  other  Marsupials) 
are  semi-oviparous,  the  young  at  birth  being  very  immature, 
and  being  therefore  taken  into  a  pouch  (in  Latin  marsupium 
signifies  pouch)  where  they  draw  nutriment  from  the  mother 
until  matured. 

Class  2.  —  Birds.  —  Warm-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  feathers,  and  the  anterior 
limbs  more  or  less  perfect  wings. 

Class  3.  —  Reptiles.  —  Cold-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  scales  or  simply  a  naked  skin. 
There  are  two  sub-classes  :  —  1.  True  Reptiles  (as  Crocodiles, 
Lizards,  Turtles,  Snakes),  which  breathe  with  lungs  (or  are 
air-breathing)  when  young  as  well  as  afterward,  being,  in  this 
respect,  like  birds  and  quadrupeds ;  2.  Amphibians  (as  Frogs 
and  Salamanders),  which  breathe  by  means  of  gills  when 
young,  and  afterward  become  air-breathing,  the  animal  under- 
going, thus,  a  metamorphosis. 

Class  4-  —  Fishes.  —  Cold-blooded  oviparous  animals, 
breathing  by  means  of  gills,  and  having  a  covering  of  scales 
or  simply  a  naked  skin.  Among  fishes  :  — 

1.  Teliosts  (as  the  Perch,  Salmon,  and  all  common  fishes) 
have  the  scales  membranous,  the  skeleton  bony,  and  the  gills 
attached  at  only  one  margin. 

The  name  is  from  the  Greek  re'Xeto?,  perfect,  and  oorreov, 
bone,  alluding  to  the  skeleton  being  all  of  it  bony. 

The  scales  in  many  are  toothed  or  set  with  spines  about 
the  inner  margin  (Fig.  50),  while  others  have  the  margin 
smooth  (Fig.  49).  Fishes  having  scales  of  the  former  kind, 
as  the  Perch,  have  been  called  Ctenoids  by  Agassiz  (from  the 
Greek  /nw,  comb) ;  and  those  having  scales  of  the  latter 
kind,  as  the  Salmon,  etc.,  Cycloids  (from  the  Greek  KVK\OV, 
circle). 

2.  Ganoids  (as   the   Gar-pike  and   Sturgeon),  having  the 


VERTEBRATES. 


51 


g,  and  the  skeleton  often  car- 


scales  bony  and  usually  sliinin 

tilaginous.     The  name  is  from  the  Greek  <yaz/o?,  shining. 

Fig.  45  represents  one  of  the  ancient  Ganoids.  The  verte- 
bral column  extends  to  the  extremity  of  the  tail,  so  that  the 
tail-fin  is  vertebrated,  while,  in  modern  Gars  and  Teliosts,  the 


Fig.  45. 


Palseouiscus  Freieslebeni  (  x 


vertebral  column  stops  at  the  commencement  of  the  tail,  or 
the  tail-fin  is  non-vertebrate  (Fig.  46).     Agassiz  called  the 


Figs.  46-54. 


GANOIDS  (excepting  49,  50).  — Fig.  46,  Tail  of  Thrissops  (x  i) ;  47,  Scales  of  Cheirolepis 
Traillii  (x  12) ;  48,  Palseoniscus  lepidurus  (x  6);  48  a,  under-view  of  same ;  49,  Scale  of  a 
Cycloid;  50,  id.  of  a  Ctenoid;  51,  Part  of  pavement-teeth  of  Gyrodus  umbilicus;  52,  Tooth 
of  Lepidosteus  ;  53,  id.  of  a  Cricodus  ;  54,  Section  of  tooth  of  Lepidosteus  osseus. 

former  kind  keterocercal,  and  the  latter  homocercal.  The 
scales  are  either  rhombic,  as  in  Figs.  45,  46,  or  rounded. 
Some  of  these  rhombic  bony  scales  are  shown  also  in  Figs. 
47,  48.  The  teeth  (Figs.  52,  53)  often  have  a  folded  or  laby- 


52 


ANIMAL  KINGDOM. 


rinthine  texture  within,  as  in  Fig.  54,  representing  a  part  of 
a  section  of  a  tooth  enlarged.  In  one  group,  the  Ganoids 
have  a  pavement  of  teeth  in  the  mouth,  as  in  Fig.  51. 

3.  Selachians  (as  the  Sharks  and  Eays),  having  a  hard  skin, 
called  shagreen,  often  rough  with  minute  points,  the  skeleton 

Pigs.  55-65. 


SELACHIANS.  —  Fig.  55,  Spinax  Blainvillii  (x  £) ;  56,  Spine  of  anterior  dorsal  fin,  natural 
size  ;  57,  Cestracion  Philippi  ( x  1) ;  58,  Tooth  of  Lainna  elegans ;  59,  Tooth  of  Carcharodon 
angustidens  ;  60,  Notidanus  priinigenius ;  61,  Hybodus  minor ;  62,  Hyb.  plicatilis  ;  63, 
Mouth  of  a  Cestracion,  showing  pavement-teeth  of  lower  jaw ;  64,  Tooth  of  Acrodus 
minimus ;  65,  Tooth  of  Acrodus  nobilis. 

more  or  less  completely  cartilaginous,  and  the  gills  attached 
by  both  margins.  The  name  is  from  the  Greek  creXa^o?,  car- 
tilage. 

Fig.  55  represents,  much  reduced,  one  of  the  order  (a  Spi- 
nax), having  the  mouth,  as  usual,  on  the  under  surface  of  the 


ARTICULATES.  53 

head,  and  remarkable  for  the  spine  before  each  of  the  back 
tins :  one  of  the  spines  is  shown,  natural  size,  in  Fig.  56. 
Fig.  57  is  an  outline  of  another  Selachian,  of  the  genus  Ces- 
tracion,  living  in  the  vicinity  of  Australia,  peculiar  in  having 
the  mouth  at  the  extremity  of  the  head,  and  also  in  the  teeth 
of  the  mouth  having,  in  part,  the  form  and  appearance  of 
a  pavement,  as  shown  in  Fig.  63.  Figs.  58  to  62  are  teeth 
of  different  Selachians  related  to  the  Sharks;  and  Figs.  64, 
65,  pavement-teeth  of  Cestraciont  species.  The  Cestraciont 
Selachians  were  once  very  common,  but  the  tribe  is  now 
nearly  extinct. 

2.    Sub-kingdom  of  Articulates. 

Among  Articulates  there  are  three  classes;  one,  including 
the  species  adapted  to  live  on  land,  and  which,  for  this  pur- 
pose, breathe  by  means  of  air-vessels  branching  through  the 
body;  and  two,  of  species  adapted  to  live  in  water,  and, 
therefore,  having  gills. 

7.  L and  Articulates,  or  the  class  of  INSECTEANS.  There  are 
three  orders  or  grand  divisions  of  Insecteans,  namely  :  1.  In- 
sects; 2.  Spiders;  3.  Myriapods  (or  Centipedes). 

2.  Water  Articulates,  including  the  two  classes  —  1.  CRUS- 
TACEANS (as  Crabs,  Lobsters,  etc.),  and  2.  WORMS. 

CRUSTACEANS. 

A  knowledge  of  the  principal  subdivisions  of  Crustaceans 
is  especially  important  to  the  student  in  geology.  There  are 
three  orders  :  — 

1.  The  Decapods,  or  W-footed  species,  as  the  Crab  (Fig.  67), 
Lobster,  Shrimp. 

2.  The  Tetradecapods,  or  I4=-footed  species,  as  the  Sow-bug 
(Fig.  68),  found  in  damp  places  under  logs,  the  Sand-flea  in 
the  sands,  or  cast-up  sea- weed  of  a  beach  (Fig.  69),  etc. 

3.  The  Entomostracans,  or  inferior  species,  having  the  feet 
defective,  as  the  Cyclops  and  related  species  (Figs.  71,  72), 
Daphnia,  Limulus  or  Horse-sJwe,  and  the  Ci/pris  and  other 


54 


ANIMAL   KINGDOM. 


Ostracoids  (Fig.  74).  These  Ostracoids  are  generally  minute 
species,  having  a  shell  like  that  of  a  bivalve  Mollusk,  as  Fig. 
74  shows ;  but  inside  of  the  shell,  instead  of  an  animal  like  a 


Pigs.  66-75. 


ARTICULATES.  —  1.  Worms :  66,  Arenicola  piscatorum,  or  Lob-worm  (x  |).  2.  Crusta- 
ceans :  67,  Crab,  species  of  Cancer ;  68,  an  Isopod,  species  of  Porcellio  ;  69,  an  Amphipod, 
species  of  Orchestia;  70,  an  Isopod,  species  of  Scrolls  (x  |);  71,  72,  Sapphirina  Irisf  71, 
female,  72,  male  (x  6);  73,  Trilobite,  Calymene  Blumenbachii ;  74,  Cythere  Americana, 
of  the  Ostracoid  family  (x  12) ;  75,  Anatifa,  of  the  Cirriped  tribe. 

clam,  there  is  one  more  like  a  shrimp,  with  jointed  legs.  The 
name  is  from  the  Greek  ocrrpaKov,  shell,  the  word  from  which 
oyster  is  derived. 

Among  Entomostracans,  there  are  also  the  Barnacles  and 
other  Cirripeds,  one  of  which  is  represented  in  Fig.  75. 

Trilobites  (Fig.  73)  are  Crustaceans  related  to  the  Entomos- 
tracans,  though  more  like  the  Tetradecapods  (Figs.  68,  70)  in 
form.  They  may  be  intermediate  between  the  two  orders. 
The  tribe  is  now  extinct. 

3.    Sub-kingdom  of  Mollusks. 

There  are  three  grand  divisions  or  classes  of  Mollusks  :  — 

1.  Ordinary  Mollusks,  as  the   Clam,  Snail,  and  Cuttle-fish, 
which  have  branchiae  (gills). 

2.  Ascidian  Mollusks,  which  have  no  branchiae  and  no  dis- 
tinct tentacles  or  arms,  and  wrhich  have  only  a  leathery  or  mem- 
branous exterior,  and  therefore  are  not  found  among  fossils. 

3.  Brachiate  Mollusks,  which  have  two  or  more  tentacles  or 


MOLLUSKS. 


55 


arms,  with  no  branching  and  which  are  usually  attached  by 
a  stem ;  many  of  which  have  two  arms  and  a  bivalve  shell, 
and  others  a  circle  or  spiral  of  tentacles  or  arms  and  thus  re- 
semble flowers  (Figs.  84,  85),  though  not  radiate  internally 
like  true  Eadiate  animals. 

1.  Ordinary  Mollusks.  —  These  are  of  three  orders  :  — 
1.  Cephalopods :  having  the  head  surrounded  by  arms,  and 
large  eyes ;  the  shell,  when  any  exists  as  an  external  covering 
for  the  body,  is,  with  a  rare  exception,  divided  internally  by 


79 


Figs.  76-85. 


MOLLUSKS.  —  1.  Cephalopods:  Fig.  76,  Nautilus,  showing  the  partitions  in  the  shell  and 
the  animal  in  the  outer  chamber.  —  2.  Gasteropods :  77,  Helix.  —  3.  Pteropods :  78,  Cleo- 
dora.  — 4.  Conchifers:  79,  80,  81,  the  last,  the  oyster. —5.  Brachiopods :  82,  Lingula,  on 
its  stem  ;  83,  Terebratula,  showing  the  aperture  at  5,  from  which  the  stem  for  attachment 
passes  out.  —6.  Bryozoans :  84,  Eschara,  with  the  animals  a  little  enlarged  ;  85,  one  of  the 
animals  out  of  the  shell,  more  enlarged. 

cross-partitions  into  a  series  of  chambers,  whence  they  are 
called  chambered  shells,  as  in  the  Nautilus  (Fig.  76)  and  Am- 
monite (page  170).  A  few  have  an  internal  chambered  shell ; 
others  an  internal  straight  bone,  which  has  sometimes  a 
conical  cavity.  The  name  is  from  the  Greek  Ke^aXrJ,  head, 
and  TroG?,  foot. 

2.  Cephalates:   having  a  head  with  distinct  eyes,  but  no 
arms  around  it,  and  usually  a  spiral  shell,  if  any;  as  the 


56  ANIMAL  KINGDOM. 

Snail  (Fig.  77)  and  other  Univalves.  The  species  of  one  di- 
vision—  that  containing  the  Snail  and  all  ordinary  Uni- 
valves —  are  called  Gasteropods,  from  the  Greek  jaarrip  and 
7rou5,  implying  that  they  crawl  on  their  ventral  surface, — • 
this  part  acting,  therefore,  as  a  foot.  In  another  division,  they 
have  a  pair  of  wing-like  oars  for  swimming,  and  these  are 
called  Pteropods  (Fig.  78),  from  the  Greek  mepov,  wing,  and 
Troi)?,  foot. 

3.  Acephals  (from  a,  without,  and  Ke<f>a\rj,  head) :  having 
no  prominent  head,  and  only  imperfect  eyes,  if  any ;  and  the 
shell  commonly  of  two  parts  called  valves,  placed  either  side 
of  the  body,  whence  the  common  name  of  most  of  the  species, 
Bivalves;  as  the  oyster,  clam  (Figs.  79-81).  These  species  are 
called  Lamellibranchs,  because  they  have  thin  lamellar  gills 
either  side  of  the  body,  from  lamella,  a  plate,  and  branchia,  a 
gill.  The  body  has  on  either  side  a  thin  fold  of  skin  called 
the  pallium  or  cloak. 

In  Fig.  79,  showing  the  inside  of  a  valve,  1,  2  are  impres- 
sions of  the  two  great  muscles  by  which  the  animal  closes  the 
shell,  and  p  p  is  the  impression  of  the  margin  of  the  mantle 
or  pallium,  called  the  pallial  impression.  This  mantle  lies 
next  to  the  shell,  and  the  shell  is  secreted  by  it;  the  gills 
are  between  it  and  the  body  of  the  Mollusk.  In  Fig.  80, 
the  pallial  impression  p  p  has  a  deep  bend  or  sinus  open- 
ing toward  the  back  margin  of  the  valve.  Shells  having 
this  sinus  in  the  impression  are  described  as  sinupallial,  and 
those  without  it  as  integripallial  In  Fig.  81,  of  the  oyster, 
there  is  but  one  large  muscular  impression  (at  2). 

2.  Brachiate  Mollusks.  —  These  are  of  two  orders  :  — 

7.  Brachiopods:  species  (Figs.  82,  83)  having  a  bivalve 
shell,  like  the  Lamellibranchs,  but  one  of  the  valves  dorsal 
(or  over  the  back),  and  the  other  ventral,  instead  of  being  on 
the  sides  of  the  body;  moreover,  the  form  is  symmetrical 
either  side  of  a  middle  line ;  that  is,  if  a  line  be  dropped 
from  the  beak  to  the  opposite  edge  (as  from  b  to  a  in  Fig. 
83),  the  parts  of  the  shell  on  the  two  sides  of  the  line  will 


RADIATES. 


57 


be  equal.  A  line  similarly  drawn  in  the  Lamellibranchs 
divides  the  valve  unequally  (as  in  Fig.  79).  The  animals 
have  two  spiral  arms  within,  which  serve  as  gills.  The 
name  Brachiopod,  from  the  Greek  fipaxifov,  arm,  and  TTOU?, 
foot,  refers  to  these  arms. 

2.  Bryozoans:  species  of  minute  size  like  a  polyp  in  exter- 
nal form,  making  often  cellular  corals  which,  though  often  in 
thin  plates  or  incrustations,  sometimes  delicately  branch  like 
a  moss,  whence  the  name,  from  the  Greek  ftpvov,  moss,  and 
doW,  animal.  They  include  the  Cellepores,  Flustras,  etc.  Fig. 
84  shows  a  number  of  the  animals  protruded  from  their  cells. 

4.    Sub-kingdom  of  Radiates. 

There  are  three  grand  divisions  of  Eadiates :  — 


Figs.  86-95. 


RADIATES.  —  1.  Echinoderms :  86,  Echinus,  the  spines  removed  from  half  the  surface 
(x  |);  87,  Star-fish,  Palaeaster  Niagarensis  ;  88,  Crinoid,  Encrinus  liliiformis ;  89,  Crinoid, 
of  the  family  of  Cystideans,  Callocystites  Jewettii.  —  2.  Acalephs :  90,  a  Medusa,  genus 
Tiaropsis  ;  91,  Hydra  (x  8)  ;  92,  Syncoryna.  —  3.  Polyps:  Fig.  93,  an  Actinia ;  94,  a  coral, 
Dendrophyllia  ;  95,  part  of  a  branch  of  a  coral  of  the  genus  Gorgonia,  showing  one  of 
the  polyps  expanded. 

1.  Echinoderms  (Figs.  86  -  89) :  having  a  more  or  less  hard, 
inflexible  exterior,  which   is   often   covered  with  spines, — 

3* 


58  ANIMAL  KINGDOM. 

whence  the  name,  from  e^o?,  a  hedgehog,  and  Sepfia,  skin. 
The  mouth  opens  downward  in  all  species  except  in  some  at- 
tached species.  Among  them  are :  7.  Echinoids,  in  which 
the  exterior  is  a  solid  shell  covered  with  spines,  and  the 
mouth  opens  downward  (Fig.  86  —  the  spines  are  removed 
from  half  of  the  shell) ;  2.  The  Asterioids,  or  Star-fishes,  in 
which  the  exterior  is  rather  stiff,  but  still  flexible,  so  that  the 
animal  flexes  it  in  its  movements  (Fig.  87)  and  the  viscera 
extend  into  the  arms ;  3.  The  Crinoids  (including  the  Coma- 
tulids),  having  flexible  arms  like  star-fishes,  but  the  rays  and 
body  made  of  closely  fitting  solid  calcareous  species,  and  hav- 
ing in  the  Comatulids  arms  for  attachment,  and  in  the  other 
Crinoids  a  stem  and  being  thus  plant-like. 

Other  kinds  are  the  RolotJmrioids,  which  are  much  like  the 
Echinoids  in  interior  structure  and  the  absence  of  arms,  but 
have  no  hard  exterior  shell,  and  are  seldom  found  fossil ;  and 
the  Ophiuroids,  or  Serpent-stars,  which  are  near  the  Asteroids, 
but  have  the  arms  very  slender,  with  no  groove  beneath. 

2.  Acalephs  (Figs.   90  -  92) :  having  a  soft,  flexible  body, 
usually  of  a  jelly-like  aspect,  though  rather  tough,  and  mov- 
ing, when  free,  with  the  mouth  downward,  as  the  Medusce 
(Fig.   90).      Some  of  the  species  called  Hydroid  Acalephs 
(Figs.  91,  92),  in  one  of  their  stages,  if  not  through  all,  look 
like  Polyps ;  and  some  of  these  Acalephs  form  corals,  like  the 
Polyps.     The  Millepores  are  Acaleph  corals.     The  other  spe- 
cies are  mostly  too  soft  to  be  common  as  fossils. 

3.  Polyps  (Figs.  93-95)  :  having  a  soft  body  usually  at- 
tached to  a  support ;  a  mouth  opening  upward  ;  one  or  more 
rows  of  tentacles  arranged  about  the  margin  of  a  disk  (some- 
what like  the  petals  of  an  Aster  around  its  central  disk) ;  and 
the  mouth  situated  at  the  centre  of  the  disk,  as  in  Fig.  93. 
Most  corals  are  made  by  polyps.     The  coral  is  secreted  with- 
in the  polyp  in  the  same  manner  as  bones  are  secreted  within 
other  animals.     Figs.  94,  95  represent  portions  of  living  cor- 
als with  the  polyps  expanded.     The  number  of  rays  in  the 
cells  of  many  modern  corals  (the  Actinoids),  is  a  multiple  of 


PROTOZOANS. 


59 


six;   and  that  in  many  of  the  more  ancient  corals,  those 
called  Cyathophylloids,  is  a  multiple  of  four. 

5.    Protozoans. 

The  principal  groups  of  Protozoans  important  to  the  geolo- 
gist are  three :  — 

1.  The  Sponges.  Sponges  contain  in  their  tissues  great 
numbers  of  minute  spicules,  which  are,  in  nearly  all  species, 
siliceous  ;  and  these  siliceous  spicules  are  found  fossil.  There 

Figs.  96-109. 


RHIZOPODS.  —  Fig.  96,  Orbulina  universa ;  97,  Globigerina  rubra  ;  98,  Textilaria  globulosa 
Ehr.  ;  99,  Rotalia  globulosa  ;  99  a,  Side-view  of  Rotalia  Boucaua ;  100,  Grammostomum 
phyllodes  Ehr. ;  101,  Frondicularia  annularis ;  102,  Triloculina  Josephina  ;  103 ,  Nodosaria 
vulgaris ;  104,  Lituola  nautiloides ;  105,  a,  Flabellina  rugosa ;  106,  Chrysalidina  gradata  ; 
107,  a,  Cuneolina  pavonia;  108,  Nummulites  nummularia;  109  a,  6,  Fusulinacylindrica. 

are  also  sponges  that  have  the  fibres  siliceous  throughout. 
(See  page  188.) 

2.  The  Rhizopods.    The  larger  part  of  them  make  calcareous 


Figs.  110-112. 

in, 


POLYCYSTINES.  —  Fig.  110,  Lychnocamtim  lucerna  (x  100);  111,  Eucyrtidium  Mongol- 
fieri(x  100);  112,  Haliralyptia  fimbriata  (X  75). 


60  VEGETABLE  KINGDOM. 

shells,  the  most  of  them  minute,  consisting  usually  of  many 
cells.  They  are  often  called  Foraminifera,  from  the  existence 
of  minute  perforations  through  the  shells.  Some  of  the  species, 
magnified  from  10  to  20  times  (excepting  the  last  two,  which 
are  of  natural  size),  are  represented  in  Figs.  96-109. 

Others  called  Polycystines  make  minute  siliceous  shells,  con- 
sisting of  many  united  cells  (Figs.  110-112).  They  differ 
from  the  other  Ehizopods,  further,  in  having  the  arrangement 
of  the  cells  radiate,  and  not  spiral  or  alternate. 

II.    Vegetable  Kingdom. 

The  vegetable  kingdom  is  not  divisible  into  sub-kingdoms 
like  the  animal ;  for  all  the  species  belong  to  one  grand  type, 
the  Radiate,  the  one  which  is  the  lowest  of  those  in  the  ani- 
mal kingdom.  The  higher  subdvisions  are  as  follow  :  — 

I.  Cryptogams.  —  Having  no  distinct  flowers  or  proper 
fruit,  the  so-called  seed  being  only  a  spore,  that  is,  a  simple 
cellule  without  the  store  of  nutriment  (albumen  and  starch) 
around  it  which  makes  up  a  true  seed ;  as  Ferns,  Sea-weed. 
They  include,  — 

1.  Thallogens,  consisting  wholly  of  cellular  tissue;   grow- 
ing in  fronds  without  stems,  and  in  other  spreading  forms ; 
as,  7.  AlgCB,  which  include  Sea-weeds  and  also  the  Confervee, 
or  Frog-spittle,  and  many  allied  fresh- water  plants ;  2.  Lichens, 
the  dry  grayish-white  and  grayish-green  plants  that  cover 
stones,  logs,  etc. ;  3.  Fungi,  including  Mushrooms,  etc. 

The  Marine  Alga:,  or  Sea-weeds,  that  are  found  fossil,  and 
are  not  microscopic  in  size,  are  mostly  of  the  tough  leathery 
kinds,  related  to  the  modern  Fuci.  They  are  often  called  by 
the  general  term  of  Fucoids,  signifying  resembling  Fuci. 

2.  Anogens,  consisting  wholly  of  cellular  tissue;  growing 
up  in  short,  leafy  stems;  as,  7.  Musci,  or  Mosses;  2.  Liver- 
worts. 

3.  Acrogens,    consisting   of  vascular   tissue   in    part,   and 
growing  upward;  as,   7.  Ferns,   or  Brakes;  2.  Lycopods,   or 
the  Ground- Pines;  3.  Equiseta,  or  the  Horse-tails. 


CRYPTOGAMS. 


61 


The  Microscopic  Algae  are  sometimes  called  ProtopJiytes. 
They  are  mostly  one-celled  species :  a  few  consist  of  a  small 
number  of  cells  united;  and  these  pass  into  other  species, 
like  common  mould,  which  are  in  threads,  simple  or  branched, 
made  up  of  many  cells.  The  kinds  found  fossil  are  the  fol- 
lowing :  — 

7.  Diatoms.  Species  having  a  siliceous  shell,  often  quite 
beautiful  in  form.  Some  of  the  shells  are  represented,  highly 
magnified,  in  Figs.  117  to  122.  They  grow  so  abundantly  in 
some  waters,  fresh  or  salt,  as  to  produce  large  siliceous  beds, 
the  material  of  which  is  an  excellent  polishing  powder,  and 
has  long  been  used  for  this  purpose. 

2.  Desmids.     Species  making  no  siliceous  shell,  consisting 
of  one  or  more  greenish  cells  (Figs.  180  — 186,  page  108). 
These  are  found  fossil  in  flint  and  hornstone. 

3.  Nullipores.     Coral-like  species,  growing  in  stout  calca- 
reous stems  or  incrusting  masses,  so-called  because  having  no 
surface  pores  or  cells. 

4.  Coccoliths.     Microscopic   calcareous   disks   occurring  in 


-,  122 


Figs.  113-122. 


PLANTS.  —  Fig.  113,  section  of  exogenous  wood ;  114,  fibres  of  ordinary  coniferous  wood 
(Pinus  Strobus),  longitudinal  section,  showing  dots,  magnified  300  times ;  115,  same  of 
the  Australian  conifer,  Araucaria  Cunningham! ;  116,  section  of  endogenous  stem. 

Figs.  117  to  122,  DIATOMS  highly  magnified;  117,  Pinnularia  peregrina,  Kichmond,  Va. ; 
118,  Pleurosigma  angulatum,  id.  ;  119,  Actinoptychus  senarius,  id.  ;  120,  Melosira  sulcata, 
id;  a,  transverse  section  of  the  same  ;  121,  Grammatophora  marina,  from  the  salt  water 
at  Stonington,  Conn.  ;  122,  Bacillaria  paradoxa,  West  Point. 

many  places  over  the  ocean's  bottom,  and  also  found  fossil. 
Named  from  KOKKOS,  seed,  and  X/#o5,  stone. 


62  VEGETABLE  KINGDOM. 

II.  Phenogams.  —  Having  (as  the  name  implies)  distinct 
flowers  and  seed ;  as  the  Pines,  Maple,  and  all  our  shade  and 
fruit  trees,  and  the  plants  of  our  gardens.  They  are  divided 
into: 

1.  Gymnosperms.  —  Having  the  flowers  exceedingly  simple, 
and  the  seed  naked,  —  the  seed  being  ordinarily  on  the  inner 
surface  of  the  scales  of  cones,  and  the  wood  having  a  bark 
and  rings  of  annual  growth  (Fig.  113) ;  as  the  Pine,  Spruce, 
Hemlock,  etc.     The  name  Gymnosperm  is  from  the  Greek 
for  naked  seed. 

The  Gymnosperms  include  (1)  the  Conifers,  or  the  Pine- 
tribe  of  plants,  usually  called  evergreens ;  and  (2)  the  Cycads, 
or  plants  related  to  the  Cycas  and  Zamia,  which  have  the 
leaves  and  look  of  a  Palm  (page  162),  although,  in  fruit  and 
wood,  true  Gymnosperms. 

The  wood  of  the  Conifers  is  simply  woody  fibre  without 
ducts,  and  in  this  respect,  as  well  as  in  the  flowers  and  seed, 
this  tribe  shows  its  inferiority  to  the  following  subdivision. 
The  fibres,  moreover,  may  be  distinguished,  even  in  petrified 
specimens,  by  the  dots  along  their  surface  as  seen  under  a 
high  magnifier.  The  dots  look  like  holes,  though  really  only 
thinner  spaces.  Fig.  114  shows  these  dots  in  the  Pinus  Stro- 
bus.  In  other  species  they  are  less  crowded.  In  one  division 
of  the  Conifers,  called  the  Araucarice,  of  much  geological  in- 
terest, these  dots  on  a  fibre  are  alternated  (Fig.  115),  and  the 
Araucarian  Conifers  may  thus  be  distinguished. 

2.  Angiosperms.  —  Having  regular  flowers  and  covered  seed  ; 
growth  exogenous,  the  plants  having  a  bark  and  rings  of 
annual  growth  (Fig.  113) ;  as  the  Maple,  Elm,  Apple,  P^ose, 
and  most  of  the  ordinary  shrubs  and  trees.     These  plants 
are  called  Angiosperms,  because  the  seeds  are  in  seed-vessels  ; 
and  also  Dicotyledons,  because  the  seed  has  two  cotyledons 
or  lobes. 

The  Gymnosperms  and  Angiosperms  make  up  the  division 
of  plants  called  Exogens,  which  is  so  named  from  the  Greek 
e£o>,  outward,  and  yevvaa),  to  grow,  because  growth  takes  place 


PHENOGAMS.  63 

through  annual  additions  of  layers  to  the  outside  of  the  trunk 
between  the  wood  and  the  bark,  as  illustrated  in  Fig.  113. 

3.  Endogens.  —  Having  regular  flowers  and  seed ;  growth 
endogenous  (from  ei/Soi>,  within,  and  yei>i>ao>),  the  plants  show- 
ing, in  a  transverse  section  of  a  trunk,  the  ends  of  fibres,  and 
no  rings  of  growth  (Fig.  116),  and  having  no  bark;  as  the 
Palms,  Rattan,  Reed,  Grasses,  Indian  Corn,  Lily.  The  Endo- 
gens  are  Monocotyledons;  that  is,  the  seed  is  undivided,  or 
consists  of  but  one  cotyledon. 


PART   III. 
HISTORICAL    GEOLOGY. 


HISTORICAL  GEOLOGY  treats  of  the  order  of  succession  in 
the  strata  of  the  earth's  crust,  and  of  the  changes  that  were 
going  on  during  the  formation  of  each  bed  or  stratum,  —  that 
is,  of  the  changes  in  the  oceans  and  the  land ;  of  the  changes 
in  the  atmosphere  and  climate ;  of  the  changes  in  the  plants 
and  animals.  In  other  words,  it  is  an  historical  view  of  the 
events  that  took  place  during  the  earth's  progress,  derived 
from  the  study  of  the  successive  rocks.  It  is  sometimes 
called  stratigrapJiical  geology;  but  this  term  embraces  only 
a  description  of  the  nature  and  arrangement  of  the  earths 
strata. 

By  using  the  means  for  determining  the  order  of  the  sev- 
eral formations  mentioned  on  page  44,  and  by  a  careful  study 
of  the  organic  remains  (as  fossils  are  often  called)  contained 
in  the  rocks,  from  the  oldest  to  the  most  recent,  it  has  been 
found  that  a  number  of  great  ages  in  the  progress  of  this  life, 
and  in  other  events  of  the  history,  can  be  made  out. 

The  following  have  thus  been  recognized :  — 

1.  There  was  first  an  age,  or  division  of  time,  when  there 
was  no  life  on  the  globe ;  or,  if  any  existed,  this  was  true 
only  in  the  later  part  of  the  age,  and  the  life  was  probably 
of  the  very  simplest  kinds. 

2.  There  was  next  an  age  when  Shells  or  Mollusks,  Corals, 
Crinoids,  and  Trilobites  abounded  in  the  oceans,  when  the 


SUBDIVISIONS  IN   THE   HISTORY.  65 

continents  were  almost  all  beneath  the  salt  waters,  and  when 
there  was,  throughout  far  the  larger  part,  as  far  as  fossils 
show,  no  terrestrial  life. 

3.  There  was  next  an  age  when,  besides  Shells,  Corals, 
Crinoids,  Trilobites,  and  Worms,  there  were  Fishes  in  the 
waters,  and  when  the  lands,  though  yet  small,  began  to  be 
covered  with  vegetation. 

4.  There  was  next  an  age  when  the  continents  were  at 
many  successive  times  largely  dry  or  marshy  land,  and  the 
land  was  densely  overgrown  with  trees,  shrubs,  and  smaller 
plants,  of  the  remains  of  which  plants  the  great  coal-beds 
were  made.     In  animal  life  there  were,  besides  the  kinds 
already    mentioned,   various    Amphibians    and    some    other 
Reptiles  of  inferior  tribes. 

5.  There  was  next  an  age  when  Reptiles  were   exceed- 
ingly abundant,  far  outnumbering  and  exceeding  in  variety, 
and  many  also  in  size  and  even  in  rank,  those  of  the  present 
day. 

6.  There  was  next  an  age  when  the  Reptiles  had  dwindled, 
and  Mammals  or  Quadrupeds  were  in  great  numbers  over  the 
continents. 

7.  After  this  came  Man;  and  the  progress  of  life  here 
ended. 

The  above-mentioned  ages  in  the  progress  of  life  and  the 
earth's  history  have  received  the  following  names  :  — 

1.  Archaean  Time  or  Age.  —  The  name  is  from  the  Greek 
for  beginning. 

2.  Age  of  Invertebrates,  or  the  Silurian  Age. 

3.  Age  of  Pishes,  or  the  Devonian  Age. 

4.  Age  of  Coal-Plants,  or  the  Carboniferous  Age. 

5.  Age  of  Reptiles,  or  the  Reptilian  Age. 

6.  Age  of  Mammals,  or  the  Mammalian  Age. 

7.  Quaternary  Age,  or  the  Age  of  Man. 

The  first  of  these  ages — the  Archcean — stands  apart  as  pre- 
paratory to  the  age  of  Invertebrates,  or  the  Silurian,  when  the 
systems  of  life,  excepting  the  Vertebrate,  were  well  displayed. 


66  HISTORICAL  GEOLOGY. 

The  Silurian,  Devonian,  and  Carboniferous  ages  were  alike  in 
many  respects,  —  especially  in  the  aspect  of  antiquity  pervad- 
ing the  tribes  that  then  lived,  the  shells,  crinoids,  corals,  fishes, 
coal-plants,  and  reptiles  belonging  to  tribes  that  are  now  wholly 
or  nearly  extinct.  The  era  of  these  ages  has,  therefore,  been 
appropriately  called  Paleozoic  time,  the  word  Paleozoic  coming 
from  the  Greek  TraXato?,  ancient,  and  ftwrj,  life. 

The  next  age  was  ushered  in  after  the  extinction  of  many 
of  the  Paleozoic  tribes ;  and  its  own  peculiar  life  approxi- 
mated more  to  that  of  the  existing  world.  Yet  it  was  still 
made  up  wholly  of  extinct  species,  and  the  most  prominent 
of  the  tribes  and  genera  disappeared  before  or  at  its  close. 
This  age  corresponds  to  Mediceval  time  in  geological  history, 
and  is  called  Mesozoic  time,  from  the  Greek  fieao?,  middle,  and 
£0)77,  life. 

The  next  age,  as  well  as  the  last,  was  decidedly  modern  in 
the  aspect  of  its  species,  the  higher  as  well  as  lower.  Both 
are  included  under  the  division  called  Cenozoic  time,  from  the 
Greek  «:a«>o<?,  recent,  and  £o>?7,  life  (the  ai  of  Greek  words 
always  becoming  e  in  English,  —  as,  for  example,  in  ether,' 
from  the  Greek  alOrip). 

The  following  are,  then,  the  grand  divisions  of  geological 
time  adopted :  — 

I.  Archaean  Time. 

II.  Paleozoic  Time,  including,  7.  The  Age  of  Invertebrates, 
or  Silurian ;  2.  The  Age  of  Fishes,  or  Devonian ;  3.  The  Age  of 
Coal-Plants,  or  Carboniferous. 

III.  Mesozoic  Time,  including  the  Reptilian  Age. 

IV.  Cenozoic  Time,  including  the  Tertiary  and  Quaternary 
Ages. 

The  following  sections  represent  the  successive  formations 
of  the  globe,  arranged  in  the  order  of  time,  with  the  subdi- 
visions corresponding  to  the  Ages  and  Periods. 


AGES. 


SUBDIVISIONS  IN   THE  HISTORY.  67 

Fig.   123.  —  PALEOZOIC.         AMERICAN  PERIODS.  FOREIGN  SUBDIVISIONS. 


Wenlock  beds. 
Upper  Llandovery 


Caradoc  sandstone. 
Bala  limestone. 
Llandeilo  group. 


Archaean 


68 


AGES. 


HISTORICAL  GEOLOG-Y. 

Fig.  123  (continued).  PERIODS.  FOREIGN  SUBDIVISIONS. 


Upper  Cretaceous. 
Middle  Cretaceous. 
Lower  Cretaceous. 


In  the  preceding  sections,  Archocan  is  at  the  bottom,  on  the 
left ;  above  it  there  are  the  names  Silurian,  Devonian,  and  so 
on ;  and  the  names  of  the  Periods,  Primordial,  Canadian, 
Trenton,  etc.,  dividing  off  these  Ages,  on  the  right. 

The  names  of  the  Periods  in  the  first  part  of  the  section 
(those  of  the  Paleozoic),  the  first  excepted,  are  derived  from 
the  names  of  American  rocks  or  localities.  The  names  on 
the  other  part  are  mostly  European,  as  the  series  of  rocks  it 
contains  (those  of  Mesozoic  and  Cenozoic  time)  are  more  com- 
plete in  Europe  than  in  America. 


SUBDIVISIONS  IN   THE   HISTORY. 


69 


70  HISTORICAL   GEOLOGY. 

The  various  strata  in  the  formations  of  an  age  are  very 
diversified  in  character,  limestones  being  overlaid  abruptly 
by  sandstones,  conglomerates,  or  shales,  or  either  of  these 
last  by  limestones ;  and  each  may  be  very  different  from  the 
following  in  its  fossils.  These  abrupt  transitions  in  the 
strata  are  proofs  that  there  were  great  changes  at  times  in 
the  conditions  of  the  region  where  the  strata  were  formed, 
and  the  transitions  in  the  kinds  of  fossils  are  evidence  of 
great  destructions  at  intervals  in  the  life  of  the  seas.  Such 
transitions,  therefore,  naturally  divide  off  the  ages  into 
smaller  portions  of  time,  or  periods,  as  they  are  called.  By 
transitions  similar  in  kind,  but  not  so  great,  periods  may 
often  be  subdivided  into  still  smaller  parts,  or  epochs. 

The  map  on  page  69  represents  the  distribution  of  the  rocks 
of  the  different  ages,  as  surface-rocks,  over  the  United  States 
and  Canada.  The  areas  indicated  by  the  different  kinds  of 
lining  are  stated  on  the  map. 

The  areas  left  white  are  of  unascertained  or  doubtful  age ; 
cr.  marks  outcrops  of  Cretaceous  on  the  Atlantic  border ; 
C.,  Cincinnati ;  CL,  Claiborne ;  V.,  Vicksburg. 

The  Silurian  strata  may  underlie  the  Devonian,  and  both 
Silurian  and  Devonian  the  Carboniferous.  The  black  areas 
of  the  Carboniferous  period  do  not,  therefore,  indicate  the 
absence  of  Devonian  and  Silurian,  but  only  that  the  Car- 
boniferous strata  are  the  surface  strata  over  the  region. 
There  may  even  be  exceptions  to  this  remark  with  regard 
to  the  surface  strata ;  for,  over  the  areas  thus  marked  Car- 
boniferous, older  rocks  may  occur  in  some  of  the  bluffs  along 
the  valleys,  or  occupy  small  areas  in  the  region,  which  are 
too  limited  to  be  noted  on  so  small  a  map. 

The  map  on  page  71  represents  the  surface-rocks  of  the 
State  of  New  York  and  Canada,  the  several  areas  corre- 
sponding to  the  periods.  For  the  Silurian,  the  lines  or  dots 
are  drawn  horizontally,  as  in  the  preceding,  and  for  the  De- 
vonian, vertically.  There  is  no  Carboniferous,  except  near 
the  southern  border  of  the  State  of  New  York. 


SUBDIVISIONS   IN   THE   HISTORY. 


71 


Geological  Map  of  New  York  and  Canada. 


72 


ARCHAEAN  TIME. 


No.  1.  The  Archaean. 

2.  The  Primordial  Period. 

3.  The  Canadian  Period. 

4.  The  Trenton  Period. 

5.  The  Niagara  Period. 

6.  The  Salina  Period. 

9.  The  Upper  Helderberg  Period. 

10.  The  Hamilton  Period. 

11.  The  Chemung  Period. 

12.  The  CatskiU  Period. 

Fig.  126. 


Lower 
Silurian. 

Tipper 
Silurian. 


Devonian. 


Silurian. 


In  the  section  in  Fig.  126,  the  rocks  of  the  successive 
periods  are  represented  in  order,  from  the  Archaean,  in  North- 
ern New  York,  southwestward  to  the  Coal-formation  of  Penn- 
sylvania, showing  that  they  succeed  one  another  on  the  map 
simply  because  they  come  to  the  surface  in  succession.  The 
amount  of  dip  and  its  regularity  are  greatly  exaggerated  in 
the  section ;  and  there  is  no  attempt  to  give  the  relative 
thickness  of  the  beds. 


GEOGRAPHICAL   DISTRIBUTION. 


73 


L—  ARCHJEAN    TIME. 
1.    Rocks:  Kinds  and  Distribution. 

1.  Distribution.  —  The  Archsean  era  commenced  with  the 
origin  of  the  earth's  crust,  and  includes  the  oldest  rocks  of 
the  globe.  Its  formations  are  those  upon  which  the  fos- 
siliferous  rocks  of  the  Silurian  and  subsequent  ages  have 
been  spread  out,  and  the  material  out  of  which  most  of 
these  later  rocks  have  been  made. 

The  Archaean  rocks  extend  around  the  whole  sphere ;  but, 

Fig.  127. 


Archaean  Map  of  North  America. 

in  general,  they  are  concealed  from  view  by  subsequent  for- 
mations. In  North  America  they  are  surface  rocks  over  a 
large  area  north  of  the  great  lakes,  shaped  like  the  letter  V, 


74  ARCHAEAN   TIME. 

the  longer  branch  of  which  area  runs  northwest  to  the  Arctic 
Ocean,  and  the  shorter,  northeast  to  Labrador.  The  white 
area  on  the  following  map,  in  what  is  now  British  America, 
is  the  portion  of  the  continent  here  referred  to.  There  is 
also  a  small  Archaean  area  in  Northern  New  York  (see  map 
page  71) ;  the  Highlands  of  Dutchess  County,  New  York,  and 
of  New  Jersey  is  Archaean,  and  so  also  in  part  the  Blue 
Ridge  of  Virginia;  another  south  of  Lake  Superior;  and  a 
few  other  spots  east  of  the  Eocky  Mountains.  Some  high 
ranges  also  of  the  Rocky  Mountain  region  are  Archaean. 

In  Europe  Archaean  rocks  are  in  view  in  the  great  iron  re- 
gions of  Sweden  and  Norway,  in  Bohemia,  and  in  Scotland. 

2.  Kinds  of  Rocks,  —  The  rocks  are  mostly  crystalline  rocks, 
such   as   granite,    syenyte,    gneiss,    syenytic    gneiss,    mica- 
schist,  hornblende  schist,  chlorite  slate,  and  granular  lime- 
stone.    But  besides  these  there  are  some  hard  conglomerates, 
quartz-rocks  or  gritty  sandstones,  and  slates.     The  beautiful 
iridescent  feldspar  called  labradorite  (page  16)  is  a  common 
constituent  of  some  of  the  coarse  crystalline  or  granitic  rocks. 

An  abundance  of  iron  is  one  characteristic  of  the  beds. 
The  rocks  very  often   contain   hornblende,  an   iron-bearing 
mineral,  or  black  mica,  also  iron-bearing.     Along  with  the 
rocks  there  are,  in  some  regions,  immense  beds  of  iron  ore 
(i  i  i,  in  Fig.  128).     In  Northern  New 
Fig.  128.  York  the  beds  are  100  to  200  feet  thick. 

Similar  iron-ore  beds  occur  in  New  Jer- 
sey, Michigan,  south  of  Lake  Superior, 
and  in  Missouri.  Graphite  is  common 
in  some  places,  and  constitutes  2  to  30 
per  cent  of  some  beds,  especially  of  the  limestones. 

3.  Disturbance  and  Crystallization  of  the  Rocks. — The  layers 
of  gneiss  and  other  schistose  rocks,  with  the  included  lime- 
stones, are  nowhere  horizontal;   but,  instead  of  this,  they 
dip  at  all  angles,  and  are  often  flexed  or  folded  in  a  most 
complex  manner.     Fig.  129  represents  the  folded  character 
of  the  Archaean  rocks  of  Canada.     The  folded  rocks  in  this 


ORIGIN   OF   THE   ROCKS.  75 

figure  are  overlaid  by  beds  that  are  nearly  horizontal,  which 
belong  to  the  Lower  Silurian. 

Owing  to  the  discolations  and  uplifts  which  the  rocks  have 
undergone,  the  iron-ore  beds  look  like  veins ;  and  even  the 
strata  of  crystalline  limestone  have  often  a  similar  vein-like 

Fig.  129. 


Fig.  129,  by  Logan,  from  the  south  side  of  the  St.  Lawrence  in  Canada,  between  Cascade 
Point  and  St.  Louis  Rapids  ;  1,  Archaean  gneiss ;  2,  2,  Silurian  strata. 

appearance.  Where  strata  have  been  thrown  up  so  that  the 
layers  stand  vertical,  the  included  bed  of  ore  will  be  vertical 
also,  and  will  descend  downward  in  the  same  manner  as  a 
true  metallic  vein ;  and  through  the  breaking  and  faulting  of 
the  strata  many  of  those  irregularities  would  result  that  are 
so  common  in  veins. 

Gneiss,  micaschist,  granular  limestone,  and  other  crystal- 
line rocks  have  been  described  on  page  23  as  metamorpliic 
rocks,  —  rocks  that  were  once  horizontal  sandstones,  shales, 
and  stratified  limestones,  and  which  have  been,  by  some  pro- 
cess, crystallized.  The  gneiss  and  schists  in  Archaean  regions, 
although  upturned  at  all  angles,  are  actually  in  layers  or 
strata  alternating  with  one  another,  as  common  with  ordinary 
sandstones  and  shales ;  and  the  ore-beds  are  conformable  to 
the  layers  of  schist  and  quartzyte  in  which  they  occur. 

4.  Conclusions  as  to  the  Origin  of  the  Rocks. —  The  following 
conclusions  hence  follow :  1.  That  the  Archa3an  rocks  here 
referred  to  were  originally  horizontal  strata  of  sandstones, 
shales,  and  limestones ;  2.  That  after  their  formation  they 
were  pushed  out  of  place  by  some  great  movement  of  the 
earth's  crust,  which  uplifted  and  folded  them,  so  that  now 
they  are  nowhere  horizontal;  3.  That,  besides  being  dis- 
placed, they  were  also  crystallized,  —  that  is,  changed  into 
metamorpkic  rocks. 

The  thickness  of  the  Archaean  rocks  of  Canada  is  stated  to 
exceed  30,000  feet.  So  great  an  accumulation  of  marine  beds 
is  proof  that  the  era  was  very  long. 


76  ARCHAEAN   TIME. 

It  is  altogether  probable  that  the  time  of  the  uplifting  and 
that  of  the  metamorphism  were  the  same.  There  may  have 
been  many  such  metamorphic  epochs  in  the  course  of  Archaean 
time.  But,  since  even  the  latest  beds  of  the  Archaean  are  thus 
upturned  and  crystallized,  an  extensive  revolution  of  this  kind 
must  have  been  a  closing  event  of  the  age.  Fig.  129  shows 
that  the  upturning  preceded  the  formation  of  the  lowest  Silu- 
rian beds,  for  these  lie  undisturbed  over  the  folded  and  crys- 
tallized Archaean. 

Below  the  surface  Archaean  rocks  there  must  be  others, 
constituting  the  interior  portions  of  the  earths  crust.  If  the 
earth  were  originally  a  melted  globe,  as  appears  altogether 
probable,  the  earth's  crust  is  its  cooled  exterior.  Whenever 
the  crust  formed,  its  surface  must  have  been  at  once  worn  by 
the  waves,  wherever  within  their  reach,  and  deposits  of  sand, 
pebbles,  and  clay  must  have  been  formed;  and  in  this  way 
the  Archaean  formations  were  begun.  But  at  the  same  time 
that  these  surface  strata  were  in  progress,  the  crust  would 
have  been  increasing  in  thickness  within  by  the  cooling 
which  was  continuing  its  progress.  Of  the  interior  rock  o*f 
the  crust  little  is  known. 

2.  Life. 

The  Archaean  rocks  contain  no  distinct  fossil-plants.  If 
plants  existed  then,  they  were  Sea-weeds;  for  remains  of 
none  higher  than  sea-weeds  occur  in  the  overlying  Lower 
Silurian  formations.  It  is  possible  that  Licliens  existed  over 
the  explored  rocks ;  for  such  plants  away  from  waters  would 
not  have  left  their  remains  in  the  mud  or  sands  of  the  seas. 
There  may  also  have  been  Fungi  of  simple  kinds.  But  there 
is  reason  to  believe  that  Mosses  and  higher  plants  were  all 
absent,  for  none  of  these  have  been  found  in  any  Lower 
Silurian  strata. 

The  graphite,  abundant  in  some  beds  in  Canada,  is  probable 
evidence  of  the  existence  of  plants,  because  it  is  known  that 


GENERAL  OBSERVATIONS* 


77 


Fig.  130. 


in  later  times  graphite  has  been  formed  out  of  their  remains. 
The  limestone  beds  suggest  the  idea  that  there  was  present 
either  vegetable  or  animal  life ;  for  almost  all  limestones  (see 
page  22)  are  of  organic  origin. 

The  annexed  figure  represents 
what  has  been  regarded  as  a  fossil 
form,  and  named  Eozoon  Cana- 
dense.  It  is  supposed  to  have 
been  a  coral-like  mass  made  by 
Protozoans  of  the  class  of  Khizo- 
pods,  the  simplest  of  all  kinds 
of  animal  life.  Each  dark  layer 
in  the  mass  is  supposed  to  mark 
the  position  of  the  animals.  Its 
animal  nature  has  not,  however, 
been  placed  beyond  doubt.  Still, 
it  is  altogether  probable  that 
Rhizopods  existed  in  the  waters  Eozoon  Canadeuse. 

before  the  close  of  the  Archaean 

era,  and  that  the  beds  of  limestone  have  been  made  of 
their  minute  shells,  or  else  of  calcareous  Nullipores. 


3.  General  Observations. 

The  large  Archaean  area  on  the  map,  page  73,  represents 
the  main  portion  of  the  dry  land  of  North  America  in  the 
later  part,  or  at  the  close,  of  the  Archaean  age ;  for  it  consists 
of  the  rocks  made  during  the  age,  and  is  bordered  on  its  dif- 
ferent sides  by  the  earliest  rocks  of  the  next  age.  It  is  the 
outline,  approximately,  of  Archcean  North  America,  or  the 
continent  as  it  appeared  when  the  Silurian  age  opened.  It 
is,  therefore,  the  beginning  of  the  dry  land  of  North  America, 
the  original  nucleus  of  the  continent.  The  smaller  Archaean 
areas  mentioned  appear  to  have  been  mountain  ridges  and 
islands  in  the  great  continental  seas. 

Europe  had  its  Archaean  lands  at  the  same  time  in  Scandi- 


78  PALEOZOIC   TIME. 

navia,  Scotland,  Bohemia,  and  some  other  points ;  and  prob- 
ably each  of  the  other  continents  was  then  represented  by  its 
spot,  or  spots,  of  dry  land.  All  the  rest  of  the  sphere,  except- 
ing these  limited  areas,  was  an  expanse  of  waters. 

The  facts  to  be  presented  under  the  Silurian  age  teach  that 
the  great  but  yet  unmade  continents,  although  so  small  in  the 
amount  of  dry  land,  were  not  covered  by  the  deep  ocean,  but 
only  by  comparatively  shallow  oceanic  waters.  They  lay  just 
beneath  the  waves,  already  outlined,  prepared  to  commence 
that  series  of  formations  —  the  Silurian,  Devonian,  Carbonif- 
erous, and  others  —  which  was  required  to  finish  the  crust  for 
its  ultimate  continental  purposes.  Portions  may  have  been 
at  times  a  few  thousands  of  feet  under  water,  but  in  general 
the  depth  was  small  compared  with  that  of  the  ocean. 

We  thus  gather  some  hints  with  regard  to  the  geography 
of  America  in  the  period  of  its  first  beginnings. 

The  outlines  of  the  Northern  Archaean  area  on  the  map, 
page  73  —  the  embryo  of  the  continent  —  and  the  directions 
of  the  other  Archaean  lands  are  very  nearly  parallel  to  the 
coast  lines  of  the  present  continent.  The  Archaean  lands, 
both  in  North  America  and  Europe,  are  largest  in  the  more 
northern  latitudes. 


II.  —  PALEOZOIC    TIME. 

PALEOZOIC  TIME  includes  three  ages :  — 

1.  The  Age  of  Invertebrates,  or  Silurian  Age. 

2.  The  Age  of  Fishes,  or  Devonian  Age. 

3.  The  Age  of  Coal-Plants,  or  Carboniferous  Age. 

In  describing  the  rocks  of  these  ages  over  North  America, 
and  the  events  connected  with  their  history,  there  are  four 
distinct  regions  to  be  noted,  —  distinct,  because  in  an  impor- 
tant degree  independent  in  their  history.  These  are,  — 

1.  The  Eastern  border  region,  or  that  near  the  Atlantic  bor- 
der, including  Central  and  Eastern  New  England,  New  Bruns- 


SILURIAN  AGE.  79 

wick  and  Nova  Scotia,,  and  the  coast  region  south  of  New 
York. 

2.  The  Appalachian  region,  or  that  now  occupied  by  the 
Appalachian  Mountain  chain,  from  Labrador  on  the  north, 
along  by  the  Green  Mountains,  and  the  continuation  of  the 
heights  through  New  Jersey,  Pennsylvania,  Virginia,  East- 
ern Tennessee,  and  so  southwestward  to  Alabama. 

3.  The  Interior  Continental  region,  or  that  west  of  the  Appa- 
lachian region,  continued  over  much  of  the  present  eastern 
slope  of  the  Eocky  Mountain  chain. 

4.  The  Western  border  and  Rocky  Mountain  region,  from  the 
crest  of  the  Rocky  Mountains  westward. 

I.   AGE   OF   INVERTEBRATES,  or  SILURIAN  AGE. 

This  Age  is  called  Silurian  from  the  region  of  the  ancient 
Silures  in  Wales,  where  the  rocks  occur.  It  was  first  so 
named  by  Murchison. 

The  Age  is  naturally  divided  into  Lower  and  Upper  Silurian, 
each  corresponding,  in  America,  to  three  periods,  thus :  — 

1.  Lower  Silurian. 

1.  Primordial,  or  Cambrian  Period :   including  the  Cam- 
brian of  England,  with  the  Lingula  flags. 

2.  Canadian  Period:   including  the  Tremadoc  slates,  the 
Skiddaw  slates,  and  Stiper-stones  group  of  Great  Britain. 

3.  Trenton  Period :    including   the   Llandeilo   flags,   Bala 
limestone,  and  Caradoc  sandstone  of  Great  Britain. 

2.  Upper  Silurian. 

1.  Niagara  Period:  including  the  Wenlock  beds  of  Great 
Britain,  with  the  Upper  Llandovery. 

2.  Salina  Period. 

3.  Lower  Helderlerg  Period :  including  part  of  the  Ludlow 
beds  of  Great  Britain. 

4.  Oriskany  Period :  including  the  upper  part  of  the  Lud- 
low beds. 


80  PALEOZOIC   TIME.  — LOWER   SILURIAN. 

1.    Primordial  Period. 
I.    Rocks:   Kinds  and  Distribution. 

The  strata  of  the  Primordial  period,  in  America,  over  the 
Interior  Continental  basin,  are  exposed  to  view  at  intervals 
from  New  York  to  the  Mississippi  Eiver ;  beyond  the  river, 
over  some  parts  of  the  eastern  and  western  slopes  of  the 
Rocky  Mountains ;  and  also  in  Texas.  The  area  on  the  map 
of  New  York  and  Canada  (page  71)  is  that  numbered  2,  lying 
next  to  the  Archaean.  There  is  reason  to  believe,  from  the 
many  points  at  which  the  strata  come  to  the  surface,  that 
they  extend  over  the  larger  part  of  the  continent  outside  of 
the  Archsean  area  represented  on  the  map,  page  73,  though 
concealed  by  other  less  ancient  strata  over  most  of  the  sur- 
face. 

Through  the  Interior  region  the  lower  rocks  are  in  part  a 
sandstone,  —  called  the  Potsdam  sandstone,  from  a  locality  in 
Northern  New  York.  The  sandstone  beds  contain,  in  many 
places,  ripple-marks  (Fig.  18,  page  33) ;  mud-cracks  (Fig.  20).; 
layers  showing  the  wind-drift  and  ebb-and-flow  structure 
(Figs.  17  /,  e) ;  worm-burrows,  and  also  occasionally  the 
tracks  of  some  of  the  animals  of  the  period. 

In  the  Appalachian  region  in  Vermont,  north  in  Canada, 
and  in  Pennsylvania,  etc.,  the  rocks  are  slates  overlying 
sandstone,  along  with  some  limestone,  the  whole  2,000  to 
7,000  feet  or  more  thick. 

In  the  Eastern  border  region  beds  of  the  period  occur  at 
Braintree,  near  Boston,  at  St.  John's,  New  Brunswick,  and 
on  the  Labrador  coast.  These  are  the  oldest  of  American 
Primordial  rocks,  and  have  been  distinctively  called  the 
Acadian  group. 

In  Great  Britain  the  Primordial  rocks  are  hard  sandstones 
and  slates.  The  uppermost  include  the  Lingula  flags.  They 
are  most  extensively  in  view  in  North  and  South  Wales  and 
in  Shropshire.  The  lower  portion  of  the  series,  of  great  thick- 


PRIMORDIAL   PERIOD.  81 

ness,  consisting  of  slates  and  other  rocks,  was  named  Cam- 
brian by  Sedgwick. 

In  Lapland,  Norway,  Sweden,  and  Bohemia,  Primordial 
strata  have  been  observed.  If  the  strata  of  later  date  could 
be  removed  from  the  continents,  we  should  probably  find  the 
Primordial  beds  extensively  distributed  over  all  the  conti- 
nents. 

2.    Life. 

These  most  ancient  of  fossiliferous  rocks  contain  no  re- 
mains of  terrestrial  life.  The  plants  of  the  period  that  have 
left  traces  in  the  rocks  were  all  Sea-weeds.  Among  animals, 
the  sub-kingdoms  of  Radiates,  Mollusks,  and  Articulates  were 
represented  by  water-species,  and  by  these  only ;  there  is  no 
evidence  that  there  were  any  Vertebrates. 

The  older  sandstone  abounds  in  many  places  in  a  shell 
smaller,  in  general,  than  a  finger-nail,  related  to  the 
modern  Lingula  (Fig.  131).     It  is  the  shell  of  a 
Mollusk  of  the  tribe  of  Brachiopods.     It  stood  on 
a  stem,  when  alive,  as  represented  in  Fig.  82,  page 
55.     These  shells  are  so  characteristic  of  the  beds 
in  many  regions  as  to  have  suggested  the  name       pm 
Lingula  flags,  or  Lingula  sandstone.     Among  Mollusks  there 
were  only  Brachiopods  for  the  greater  part  of  the  Primordial 
period ;  but  in  the  later  division  appear  some  species  of  La- 
mellibranchs,  Pteropods,  Gasteropods,  and  Cephalopods. 

Another  tribe  very  prominent  among  the  earliest  of  the 
earth's  animals  is  that  of  Trilobites,  of  the  sub-kingdom  of 
Articulates,  and  class  of  Crustaceans. 

One  of  the  largest  of  them,  and  a  kind  characteristic  of  the 
Lower  or  Acadian  division  of  the  Primordial,  is  represented 
in  Fig.  132,  one  sixth  the  natural  size.  Its  total  length,  when 
living,  must  have  been  eighteen  inches  or  more,  and  hence  it 
was  about  as  large  as  any  living  Crustacean.  The  specimen 
figured  was  found  at  Braintree,  south  of  Boston.  As  shown, 
it  had  large  eyes  situated  on  the  head-shield,  —  evidence, 


82 


PALEOZOIC   TIME.  — LOWER  SILURIAN. 


Pig.  132. 


as  Buckland  observed,  of  the  clear  waters  and  clear  skies 

of  Primordial  time.  As  no  legs  are  ever  found  in  connec- 
tion with  Trilobites,  they  are 
supposed  to  have  had  only  thin 
membranous  or  foliaceous  plates 
for  swimming.  Tig.  133  shows 
the  track  of  a  large  animal  (re- 
duced to  one  sixth)  found  by 
Logan  in  the  Canada  beds, 
which  may  have  been  made 
by  one  of  the  great  Trilobites 
as  it  crawled  over  the  sand. 

The  existence  of  marine  worms 
among  the  earliest  animals  of 
the  globe  is  proved  by  the 
great  numbers  of  worm-holes 
or  burrows  in  the  sandstones, 
now  filled  with  hard  sandstone 
like  that  of  the  rock.  They 
are  very  similar  to  the  holes- 
made  by  such  worms  in  the 
sands  of  sea-shores  at  the  pres- 
ent time.  One  species  has  been 
called 

Scolitkus  linearis.    These  worm-holes 

are   common   in    the   European   as 

well  as  American  Primordial  sand- 
stones. 

There  were  also  Crinoids  of  the 

sub-kingdom  of  Eadiates  (page  58), 

for    disks   from   the   broken   stems 

of    Crinoids    are    not    uncommon. 

And  among  Protozoans  there  were 

Sponges,   and   probably  the  minute 

Rhizopods  (page  59). 

Sponges    among    Protozoans,    Crinoids    among    Radiates, 


TRILOBITE.  —  Paradoxides  Harlani 
(X  ft 


Fig.  133. 


Track  of  a  Trilobite  (x  ft 


PRIMORDIAL  PERIOD.  83 

Brachiopods  and  some  representatives  of  other  tribes  among 
Mollusks,  Worms  and  Trilobites  among  Articulates,  and  Sea- 
weeds among  Plants,  made  up  the  living  species  thus  far  dis- 
covered; and  in  this  Primordial  population,  Trilobites  took 
the  lead.  There  is  as  yet  no  evidence  that  the  dry  Primor- 
dial hills  bore  a  Moss  or  Lycopod,  or  harbored  the  meanest 
Insect,  or  that  the  oceans  contained  a  single  Fish. 

3.   General  Observations. 

The  ripple-marks,  mud-cracks,  and  tracks  of  animals  pre- 
served in  this  most  ancient  of  Paleozoic  rocks  are  records 
left  by  the  waves,  the  sun,  and  the  life  of  the  period,  as  to 
the  extent  and  condition  of  the  continent  in  that  early  era. 
These  markings  teach  that  when  the  beds  were  in  progress 
a  large  part  of  the  continent  lay  at  shallow  depths  in  the 
sea,  so  shallow  that  the  waves  could  ripple  its  sands ;  that 
over  other  portions  the  surface  was  a  sand-flat  exposed  at 
low  tide  ;  or  a  sea-beach,  the  burrowing-place  of  worms ; 
or  a  mud-flat,  that  could  be  dried  and  cracked  under  the 
heat  of  the  sun,  or  in  a  drying  atmosphere. 

With  such  evidences  of  shallow  water  or  emerged  flats 
in  a  formation  extending  widely  over  the  continent,  it  is  a 
safe  conclusion  that  the  North  American  continent  was 
at  the  time  in  actual  existence,  and  probably  not  far  from 
its  present  extent ;  and,  although  partly  below  the  sea-level, 
and  in  some  places  deeply  so,  it  was  generally  at  shallow 
depths.  The  same  may  prove  to  have  been  true  of  the  other 
continents.  There  is,  in  fact,  evidence  of  other  kinds  which, 
taken  in  connection  with  the  above,  leaves  little  doubt  that 
the  existing  places  of  the  deep  ocean  and  of  the  continents 
were  determined  even  in  the  first  formation  of  the  earth's 
crust  in  the  early  Archaean  era,  and  that,  in  all  the  move- 
ments that  have  since  occurred,  the  oceans  and  continents 
have  never  changed  places. 

This  preservation  of  markings,  seemingly  so  perishable,  on 
the  early  shifting  sands,  is  a  very  instructive  fact.  They 


84  PALEOZOIC   TIME.  — LOWER   SILURIAN. 

illustrate  part  of  the  means  by  which  the  earth  has,  through 
time,  been  recording  its  own  history.  The  track  of  a  Trilo- 
bite,  or  of  a  wavelet,  is  a  mould,  in  sand  or  earth,  into  which 
other  sands  are  cast  both  to  copy  and  preserve  it ;  for  if  the 
waves  or  currents  that  succeed  are  light,  they  simply  spread 
new  sands  over  the  indented  surface,  without  obliterating 
the  mould ;  and  so  the  addition  of  successive  layers  only 
buries  the  markings  more  deeply  and  thus  protects  them 
against  destruction.  When,  finally,  consolidation  takes 
place,  the  track  or  ripple-mark  is  made  as  enduring  as 
the  rock  itself. 

After  the  formation  in  North  America  of  the  great  Primor- 
dial sandstone,  there  was  a  change  in  the  condition  of  the 
surface,  especially  over  the  interior  of  the  continent.  For 
limestone  strata  began  then  to  form  where  sandstones  were 
in  progress  before.  This  change  was  probaby  some  increase 
in  the  depth  and  clearness  of  the  Interior  Continental  sea. 
Along  the  borders  of  this  sea  —  that  is,  in  New  York  and 
along  the  Appalachian  region  from  Quebec  into  Virginia  — 
the  rock  was  a  sandstone  or  shale,  with  some  subordinate 
strata  of  limestone. 


2.    Canadian  and  Trenton  Periods. 

The  CANADIAN  period  is  so  named  from  Canada,  where 
the  rocks  are  well  displayed  and  have  been  most  thoroughly 
studied;  and  the  TRENTON  period,  from  Trenton  Falls,  just, 
north  of  Utica,  the  river  at  the  Falls  running  between 
high  bluffs  of  Trenton  limestone. 

In  Great  Britain  the  first  of  these  periods  covers  the  era 
of  the  Tremadoc  and  Skiddaw  slates,  and  the  latter  that  of 
the  Bala  limestone  and  Llandeilo  flags. 

I.    Rocks:   Kinds  and  Distribution. 

In  the  Primordial  period  the  rock  deposits  formed  over  the 
North  American  continent  were  mainly  of  sands  or  mud, 


CANADIAN   AND   TRENTON   PERIODS.  85 

making  sandstones  and  shales ;  and  but  little  limestone  was 
formed.  The  Canadian  period  is  one  of  transition  to  a  third, 
the  Trenton,  when  limestones  were  in  progress  over  nearly 
the  whole  breadth  of  the  continent,  the  Appalachian  and 
Arctic  regions,  as  well  as  the  Interior  Continental. 

The  rocks  of  the  Canadian  period  to  the  eastward  in  New 
York  and  Canada  are,  —  1.  A  sandstone  associated  in  places 
with  much  limestone,  and  called,  in  allusion  to  the  limestone, 
the  Calciferous  sand-rock ;  2.  South  of  Quebec,  shale,  sand- 
stone, and  thin  beds  of  limestone,  called  the  Quebec  group ; 
3.  A  limestone  formation,  called  the  Chazy  limestone,  from  a 
place  of  that  name  in  Northern  New  York.  The  latter  lime- 
stone (with  probably  beds  of  the  Quebec  group)  makes  part 
of  the  granular  limestone  or  marble  of  the  Green  Mountains 
from  Vermont  to  Connecticut,  and  has  great  thickness  also  in 
Pennsylvania  and  Virginia.  In  the  Interior  basin  the  rock 
of  the  period  is  mainly  limestone  —  in  Iowa  and  Wisconsin 
the  Lower  Magnesian  limestone  —  excepting  to  the  north, 
where  the  upper  part  is  sandstone  (St.  Peter's  sandstone)  and 
along  the  south  side  of  Lake  Superior,  where  there  is  only 
sandstone.  The  "  Pictured  Kocks  "  are  included  in  it ;  and 
the  thick  sandstones  of  Keweenaw  Point,  remarkable  for 
their  intersection  by  trap  dikes  and  veins  of  copper,  are  sup- 
posed to  be  of  the  same  period. 

The  Trenton  period  is  the  most  remarkable  limestone-mak- 
ing era  in  American  geological  history.  The  rock,  unlike 
the  Lower  Magnesian  limestone,  is  generally  full  of  fossils,  — 
shells,  crinoidal  remains,  corals,  etc. ;  and  often  these  fossils 
are  so  crowded  together  that  no  spot  so  large  as  the  end  of 
the  finger  can  be  found  without  one  or  more  of  them.  The 
"  Birdseye  "  and  "  Black  Eiver "  limestones  are  the  lower 
strata  in  succession  of  the  Trenton  period.  The  upper  part 
of  the  limestone  (marble)  of  the  Green  Mountains  is  probably 
Trenton.  The  rock  of  the  latter  part  of  the  Trenton  period 
(called  the  Cincinnati  epoch),  in  New  York  and  the  Appala- 
chians, is  shale  and  sandstone,  and  even  in  the  Interior 


86  PALEOZOIC   TIME.  —  LOWER  SILURIAN. 

basin  the  limestones  are  often,  as  about  Cincinnati,  quite 
clayey  or  impure.  The  Utica  shale,  Lorraine  shale,  and  a 
small  portion  of  the  Hudson  Eiver  shale  of  New  York, 
belong  to  this  era.  In  the  Green  Mountains,  instead  of 
shales  and  earthy  sandstones,  there  are  gneiss,  micaschist, 
quartzyte,  etc. 

The  thickness  of  the  rocks  of  the  Canadian  and  Trenton 
periods  in  Pennsylvania  is  over  7,500  feet ;  while  in  Illinois 
it  is  but  750  feet,  and  in  Missouri  about  2,000  feet. 

The  rocks  of  this  era  in  Great  Britain  are  shales  and  shaly 
sandstones,  with  but  little  limestone.  The  Tremadoc  slates 
are  dark  slates  over  1,000  feet  thick  in  Wales,  passing  below 
into  the  Lingula  flags,  and  above  into  the  Llandeilo  beds.  The 
Llandeilo  flags  are  shaly  sandstones ;  and,  together  with  the 
associated  shales,  they  have  a  thickness  of  many  thousand 
feet.  Above  them  there  are  the  Caradoc  sandstone  of  Shrop- 
shire, and  the  Bala  formation,  the  latter  sandy  slates  and  sand- 
stone, with  thin  beds  of  limestone,  in  Wales.  In  Scandinavia 
the  rocks  are  limestone,  overlaid  by  slates  and  flags ;  and  in 
the  Baltic  provinces  of  Russia  —  part  of  the  Interior  Conti- 
nental portion  of  the  Eastern  Continent  —  they  are  mainly 
limestones. 

2.    Life. 

The  life  of  these  periods,  like  that  of  the  Primordial,  was, 
as  far  as  evidence  has  been  collected  from  the  American  or 
foreign  rocks,  wholly  marine :  no  trace  of  a  terrestrial  or 
fresh-water  species  of  plant  or  animal  has  been  found. 

The  plants  found  fossil  are  Sea-weeds. 

All  the  sub-kingdoms  of  animals  were  represented,  with  the 
exception  of  the  Vertebrates.  Among  Radiates  there  were 
Corals  and  Crinoids ;  among  Mollusks,  representatives  of  all 
the  several  orders;  among  Articulates,  the  water-divisions, 
Worms  and  Crustaceans. 

1.  Radiates,  —  The  Canadian  beds,  especially  the  finer 
slates  and  shales,  are  remarkable  for  the  great  abundance 


CANADIAN   AND   TRENTON   PERIODS. 


87 


of  very  delicate  plume-like  remains  of  Eadiate  life,  called 
Graptolites,  from  the  Greek  jpdcf)a),  I  write. 


GRAPTOLITES.  —  Fig.  134,  Graptolithus  Logani,  the  central  portion  of  a  radiating  group 
of  stems  with  parts  of  the  stems  ;  135,  same,  portion  of  one  of  the  stems,  and  135  a,  part 
of  steins  enlarged;  136,  Graptolithus  pristis ;  137,  138,  Phyllograptus  typus;  139,  the 
young  of  a  Graptolite. 

A  few  of  the  kinds  are  represented  in  Figs.  134,  135,  137- 
139,  and  one  species,  from  the  later  part  of  the  Trenton 
period,  in  Fig.  136.  In  the  living  state  there  were  cells 
along  the  notched  margin,  one  for  each  notch,  from  which 
little  star-shaped  animals  extruded  themselves.  They  be- 
long to  the  tribe  of  Hydroids,  under  Acalephs,  described 
on  page  58. 

Fig.  140  represents  one  of  the  Corals  of  the  Trenton.  Its 
shape  is  that  of  a  curved  cone,  a  little  like  a  short  horn,  the 
small  end  being  the  lower.  At  top,  when  perfect,  the  cavity 
of  the  coral  is  divided  off  by  plates  radiating  from  the  centre. 
Such  corals  are  called  CyathopJiylloid  corals,  from  the  Greek 
/cvaOos,  cup,  and  $>v\\ov,  leaf,  alluding  to  the  cup  full  of  radi- 
ating leaves  or  plates.  When  living,  the  coral  occupied  the 
interior  of  an  animal  similar  to  that  represented  in  Fig.  93  or 
Fig.  94  on  page  57. 

Another  kind  of  coral,  of  a  hemispherical  form,  and  made 
up  of  very  fine  columns,  is  represented  in  Figs.  141,  142,  the 
latter  showing  the  interior  appearance.  It  is  called  Chcetetes 
lycoperdon.  Another,  of  coarser  columns,  —  each  nearly  a 
sixth  of  an  inch  in  diameter, — is  called  the  Columnaria  alveo- 


88 


PALEOZOIC   TIME.  —  SILURIAN. 


lata.  In  a  transverse  section  the  columns  are  divided  off  by 
horizontal  partitions.  Masses  of  this  coral  have  been  found 
that  weigh  each  between  two  and  three  thousand  pounds. 

Fig.  143  shows  the  form  of  one  of  the  Crinoids,  though  the 
stem  on  which  it  stood  is  mostly  wanting,  and  the  arms  are 
not  entire.  The  mouth  was  in  the  centre  above,  and  the  ani- 
mal was  related  to  the  Comatula  among  star-fishes,  from 
which  it  differed  in  being  attached  to  the  sea-bottom  by  means 
of  a  jointed  stem.  There  were  also  true  star-fishes  in  the  seas. 

Figs.  140-151. 

143 


RADIATES  OF  THE  TRENTON  PERIOD.  — Fig.  140,  Petraia  corniculum  ;  141,  142, 
Chsetetes  lycoperdon ;  143,  Lecanocrinus  elegans.  —  MOLLUSKS :  Fig.  144,  Ptilodictya 
acuta ;  145,  Orthis  testudinaria ;  146,  Orthis  occidentalis ;  147,  Leptsena  sericea ;  148, 
Avicula  (?)  Trentonensis ;  149,  Pleurotomaria  lenticularis ;  150,  Orthoceras  junceum.  — 
ARTICULATES  :  Fig.  151,  Asaphus  gigas. 

2.  Mollusks.  —  Among  Mollusks  Bryozoans  were  very  com- 
mon :  the  fossils  are  small  cellular  corals :  one  is  shown  in 
Fig.  144.  Brachiopods  were  still  more  characteristic  of  the 


CANADIAN  AND   TRENTON  PERIODS.  89 

period,  and  occur  in  vast  numbers.  Fig.  145  is  Orthis  testudi- 
naria;  Fig.  146,  0.  occidentalis  ;  Fig.  147,  Leptcena  sericea. 
There  were  also  some  Lamellibranchs,  as  Fig.  148,  Avicula  ? 
Trentonensis ;  and  some  Gasteropods,  as  Fig.  149,  Pleuroto- 
maria  lenticularis.  Shells  of  Cephalopods  were  especially 
common  under  the  form  of  a  straight  or  curved  horn  with 
transverse  partitions.  Fig.  150,  Orthoceras  junceum,  repre- 
sents a  small  species.  One  kind  had  a  shell  12  or  15  feet 
long  and  nearly  a  foot  in  diameter.  The  word  Orthoceras  is 
from  the  Greek  o/o#o9,  straight,  and  ice  pas,  horn. 

There  were  some  species  also  of  the  genus  Nautilus. 

3.  Articulates.  —  Fig.  151  represents  one  of  the  large  Trilo- 
bites  of  the  Trenton  rocks,  the  Asaphus  gigas,  —  a  species 
sometimes  found  a  foot  long.  Another  Trilobite  is  the  Caly- 
mene  Blumenbachii,  represented  in  Fig.  73,  page  54. 

While  Trilobites  appear  to  have  been  the  largest  and  high- 
est life  of  the  Primordial  seas,  Cephalopods,  of  the  Orthoceras 
family,  far  exceeded  Trilobites  in  both  respects  in  the  Trenton. 
The  larger  kinds  must  have  been  powerful  animals  to  have 
borne  and  wielded  a  shell  12  or  15  feet  long.  Although 
clumsy  compared  with  the  fishes  of  a  later  age,  they  emu- 
lated the  largest  of  fishes  in  size,  and  no  doubt  also  in  their 
voracious  habits.  Crustaceans,  in  their  highest  divisions,  as 
the  Crabs,  may  perhaps  be  regarded  by  some  as  of  superior 
rank  to  Cephalopods.  But  Trilobites,  of  the  inferior  division 
of  Crustaceans,  without  proper  legs,  living  a  sluggish  life  in 
slow  movement  over  the  sands  or  through  the  shallow  waters, 
or  skulking  in  holes,  or  attached  like  limpets  to  the  rocks, 
were  far  inferior  species  to  the  Cephalopods. 

3.    General  Observations. 

1.  Geography.  —  The  wide  continental  region  covered  by  the 
Trenton  limestone  formation,  stretching  over  the  Appalachian 
region  on  the  east,  and  widely  through  the  Interior  basin, 
must  have  been  throughout  a  clear  sea,  densely  populated 
over  its  bottom  with  Brachiopods,  Corals,  Crinoids,  Trilobites, 


90  PALEOZOIC   TIME. 

and  the  other  life  of  the  era.  It  may,  however,  have  been  a 
shallow  sea ;  for  the  corals  and  beautiful  shells  of  coral  reefs 
live  mostly  within  100  feet  of  the  surface. 

During  the  later  part  of  the  period,  or  that  of  the  Cincin- 
nati group,  the  same  seas,  especially  on  the  north,  became 
more  open  to  sediment,  through  some  change  of  level  or  of 
coast-barriers,  and  consequently  much  of  the  former  life  dis- 
appeared, and  other  kinds,  adapted  to  impure  waters  or  to 
muddy  bottoms,  supplied  their  places. 

2.  Disturbances  during  the  Lower  Silurian,  and  at  its  Close.  — 
7.  Igneous  ejections  in  the  Lake  Superior  district.  —  During  the 
progress  of  the  Canadian  period  there  were  extensive  igneous 
ejections  through  fractures  of  the  earth's  crust  in  the  vicinity 
of  Lake  Superior,  about  Keweenaw  Point  and  elsewhere ;  and 
probably  to  some  extent  also  over  the  bottom  or  area  of  the 
lake  itself,  for  this  is  indicated  by  the  dikes  and  columnar 
trap  of  Isle  Koyale,  an  island  in  the  lake.  These  rocks,  which 
were  melted  when  ejected,  now  stand  in  many  places  in  bold 
bluffs  and  ridges ;  and  mixtures  of  scoria  and  sand  make  up 
some  of  the  conglomerate  beds  of  the  region.  The  sandstones,, 
penetrated  by  the  dikes  of  trap,  and  made  partly  before  and 
partly  after  the  ejection,  have  a  thickness  in  some  places  of 
six  or  eight  thousand  feet.  There  appears  to  have  been  a 
sinking  of  the  region  equal  to  the  thickness  of  the  beds,  in 
addition  to  the  igneous  ejections.  The  great  veins  of  native 
copper  of  the  Lake  Superior  region  are  part  of  the  results  of 
this  period  of  disturbance. 

2.  Emergence  of  the  region  of  the  Green  Mountains.  —  The 
changes  from  deep  to  shallow  seas,  or  partly  emerged  flats, 
during  the  Silurian  era,  are  evidence  that  changes  of  level, 
by  gentle  movements  or  oscillations  in  the  earth's  crust,  were 
going  on  throughout  it.  But  after  the  Lower  Silurian  had 
closed  there  appear  to  have  been  greater  and  more  permanent 
changes.  The  valley  of  Lake  Champlain  and  the  Hudson,  as 
shown  by  Logan,  probably  dates  from  this  time.  The  Green 
Mountains  were  probably  then  made  and  became  part  of  the 


LOWER  SILURIAN.  91 

stable  dry  land,  like  the  Archaean  regions.  (See  map,  page  73.) 
That  they  were  not  dry  land  before  is  shown  by  the  Chazy^ 
and  Trenton  limestones  in  their  structure,  for  these  are  of 
marine  origin ;  and  that  the  region  was  above  the  water  from 
and  after  this  time  is  indicated  by  the  fact  that  the  Trenton 
formations  were  the  latest  there  formed,  and  by  the  still  more 
important  observation  that  near  Hudson,  in  the  Hudson  River 
valley,  and  near  Bernardston,  in  the  Connecticut  Valley,  there 
are  Upper  Silurian  rocks  overlying  unconformably  the  up- 
turned older  rocks. 

During  the  progress  of  the  Lower  Silurian  era  a  great  thick- 
ness of  rock  had  been  made  over  the  Green  Mountain  region, 

—  probably  15,000  or  20,000  feet.    These  beds  were  laid  down, 
not  in  a  sea  15,000  or  20,000  feet  deep  until  it  was  full,  but 
in  shallow  waters  over  a  bottom  that  was  gradually  sinking, 

—  and  so  gradually  that  the  rock-material  accumulating  over 
it  kept  it  shallow.     Then,  when  the  slowly  forming  trough 
had  reached  this  depth,  the  epoch  of  catastrophe,  that  is,  of 
mountain-making,  began  when  the  beds  were  displaced  and 
folded,  and  consolidated  or  crystallized.    Quartzose  sandstones 
were  changed  to  hard  quartzyte,  —  the  rock  of  high  ridges  in 
Berkshire  and  Vermont ;  earthy  sandstones  were  made  into 
mica-schist  and  gneiss;   and  common  limestones   came  out 
white  or  clouded  marbles,  now  extensively  quarried  for  archi- 
tectural purposes  in  Canaan,  Connecticut,  Berkshire  County 
in  Massachusetts,  and  at  Eutland  and  elsewhere  in  Vermont. 
Thus,  this  northern  end  of  the  Appalachian  region  was  the 
first  of  it  to  be  made  into  mountains  and  become  part  of  the 
stable  land ;  the  rest  of  it  to  the  south,  as  well  as  the  cen- 
tral region  of  Southern  New  York,  was  still  receiving,  for  a 
long   era   afterward,  new  formations,  and  so  preparing  for 
another  time  of  mountain-making,  —  that  of  the  Alleghany 
range. 

Besides  this  uplifting  and  upturning  in  Western  New  Eng- 
land, there  was  at  the  same  time,  as  shown  by  Safford  and 
Newberry,  a  bending  upward  of  the  Lower  Silurian  beds  along 


92  PALEOZOIC  TIME. 

a  region  extending  southwestward  from  Lake  Erie  over  Cin- 
^innati  through  Kentucky,  which  area  was  partly  an  emerged 
peninsula  or  island  through  the  rest  of  Paleozoic  time. 

In  Great  Britain  and  Europe  also  there  were  disturbances 
at  the  close  of  the  Lower  Silurian.  The  range  of  Southern 
Scotland  has  been  referred  to  this  epoch,  and  so  also  the 
Westmoreland  Hills,  and  mountains  in  North  Wales,  and 
hills  in  Cornwall. 

3.  Life.  —  There  is  no  evidence  that  the  system  of  life  in 
its  progress  during  the  Lower  Silurian  had  so  far  advanced  as 
to  include  a  terrestrial  species,  or  the  lowest  of  Vertebrates. 
Trilobites  held  the  first  position  in  the  Primordial  Period,  Or- 
thocerata  and  other  Cephalopods  in  the  Trenton.  Among 
Articulates  there  were  neither  Myriapods,  Spiders,  nor  In- 
sects as  far  as  discovered ;  for  these  are  essentially  terrestrial 
animals,  and  the  first  species  of  them  thus  far  found  are  of 
Devonian  age. 

Among  the  genera  of  the  Lower  Silurian,  only  four  have 
living  species.  These  are  Discina,  RJiyncJwnella,  and  Crania 
among  Brachiopods,  and  Nautilus  among  Cephalopods.  Lin- 
gula  is  supposed  by  some  to  be  another  of  this  group ;  but 
others  make  the  Silurian  species  of  another  genus.  These 
genera  of  long  lineage  thus  reach  through  all  time  from  the 
Lower  Silurian  onward.  All  other  genera  disappear,  —  some 
at  the  close  of  the  Primordial,  others  at  that  of  the  Canadian 
or  Trenton  period,  and  some  at  the  termination  of  subordinate 
epochs  within  these  periods. 

The  extermination  of  species  took  place  at  intervals 
through  the  periods,  as  well  as  at  their  close ;  though  those 
at  the  latter  were  most  universal.  With  the  changes  from 
one  stratum  to  another  there  were  disappearances  of  some 
species,  and  with  the  changes  from  one  formation  to  another 
still  larger  proportions  became  extinct.  No  Primordial  spe- 
cies are  known  to  occur  in  the  Canadian  period ;  very  few  of 
the  species  of  the  Canadian  period  survive  into  the  Trenton ; 
and  very  many  of  those  of  the  early  part  of  the  Trenton  did 


UPPER  SILURIAN.  93 

not  exist  in  the  later  part.  Thus  life  and  death  were  in  pro- 
gress together,  species  being  removed,  and  other  species  ap- 
pearing as  time  moved  on. 

3.    Upper  Silurian  Era. 
I.    Subdivisions. 

The  Upper  Silurian  era  in  North  America  includes  four 
periods :  the  NIAGARA,  the  SALINA,  the  LOWER  HELDERBERG, 
and  the  ORISKANY.  The  name  of  the  first  is  from  the  Niagara 
River,  along  which  the  rocks  are  displayed ;  that  of  the  second, 
from  Salina  in  Central  New  York,  the  beds  being  the  salt- 
bearing  rocks  of  that  part  of  the  State ;  that  of  the  third, 
from  the  Helderberg  Mountains,  south  of  Albany,  where  the 
lower  rocks  are  of  this  period ;  that  of  the  fourth,  from  Oris- 
kany,  a  place  in  Central  New  York,  northwest  of  Utica. 

2.    Rocks:   Kinds  and  Distribution. 

The  rocks  of  the  Niagara  period  are  :  1.  A  conglomerate 
and  grit-rock  called  the  Oneida  conglomerate,  which  extends 
from  Central  New  York  southward  along  the  Appalachian 
region,  having  a  thickness  of  700  feet  in  some  parts  of  Penn- 
sylvania ;  together  with  shaly  sandstones  of  the  Medina  group, 
which  spread  westward  from  Central  New  York  through 
Michigan,  and  also  southward  along  the  Appalachian  region, 
being  1,500  feet  thick  in  Pennsylvania ;  2.  Hard  sandstones, 
or  flags  and  shales  of  the  Clinton  group,  having  nearly  the 
same  distribution  as  the  Medina  formation,  though  a  little 
more  widely  spread  in  the  west,  and  about  2,000  feet  thick 
in  Pennsylvania ;  3.  The  Niagara  group,  occurring  in  Western 
New  York,  and  extending  widely  over  both  the  Appalachian 
and  Interior  Continental  regions :  it  consists,  at  Niagara,  of 
shales  below  and  thick  limestone  above ;  mainly  of  limestone 
in  the  Interior  region ;  and  of  clayey  sandstone  or  shales  in 
the  Appalachian  region,  where  it  has  a  thickness  of  1,500 
feet  or  more.  The  Niagara  is  one  of  the  great  limestone 


94  PALEOZOIC   TIME. 

formations  of  the  continent,  existing  also  in  the  Arctic 
regions. 

Ripple-marks  and  mud-cracks  are  very  common  in  the 
Medina  formation.  The  example  of  rill-marks  figured  on 
page  33  is  from  its  strata  in  Western  New  York. 

The  Salina  rocks  are  fragile,  clayey  sandstones,  marlytes, 
and  shales,  usually  reddish  in  color,  and  including  a  little 
limestone.  They  occur  in  New  York  and  sparingly  to  the 
westward,  being  thickest  (700  to  1,00(3  feet  thick)  in  Onon- 
daga  County,  New  York. 

The  salt  of  Salina  and  Syracuse,  in  Central  New  York,  is 
obtained  from  wells  of  salt  water  150  feet  and  upward  in 
depth,  which  are  borings  into  these  saliferous  rocks.  From  35 
to  45  gallons  of  the  water  afford  a  bushel  of  salt,  while  of  sea- 
water  it  takes  350  gallons  for  the  same  amount.  No  salt  is 
there  found  in  solid  masses,  but  near  Goderich,  in  Canada, 
at  a  depth  of  about  1,000  feet,  there  is  a  bed  of  rock-salt  14 
to  40  feet  thick.  Gypsum  is  common  in  some  of  the  beds. 
The  lower  beds  are  the  water-lime  group,  the  limestone 
being  hydraulic  (page  25). 

The  Lower  Helderberg  group  consists  mainly  of  limestones, 
and  is  the  second  limestone  formation  of  the  Upper  Silurian. 
The  formation  is  well  developed  in  the  State  of  New  York 
and  along  the  Appalachian  region  to  the  south ;  it  also  occurs 
in  Ohio,  Indiana,  Southern  Illinois,  and  Tennessee ;  also 

Fig.  152. 


w 

Section  along  the  Niagara,  from  the  Falls  to  Lewiston  Heights. 

along  the  Connecticut  Valley,  in  Northern  Maine,  and  in 
New  Brunswick  and  Nova  Scotia. 

The  section,  Fig.  152,  represents  the  rocks  on  the  Niagara 


UPPER  SILURIAN.  95 

\ 

Eiver  at  and  below  the  Falls.  The  Falls  are  at  F ;  the  whirl- 
pool, three  miles  below,  at  W ;  and  the  Lewiston  Heights, 
which  front  Lake  Ontario,  at  L.  Nos.  1,  2,  3,  4  are  different 
sandstone  strata  belonging  to  the  Medina  group;  5,  shale, 
and  6,  limestone,  to  the  Clinton  group ;  7,  shale,  and  8,  lime- 
stone, to  the  Niagara  group.  The  next  section  (Fig.  153), 

Fig.  153. 


56  oo  ott  t> 

Section  of  the  Salina  and  underlying  strata,  from  north  to  south,  south  of  Lake  Ontario. 

from  the  region  south  of  the  eastern  part  of  Lake  Ontario, 
consists  as  follows :  5  b,  Medina  group,  5  c,  Clinton  group, 
5d,  Niagara  group  (shale  and  limestone),  6,  Salina  beds. 
(Hall.) 

The  Oriskany  beds  are  mostly  rough  sandstones.  The  for- 
mation extends  from  Oriskany,  New  York,  southward  along 
the  Appalachian  region  through  Pennsylvania,  Maryland,  and 
Virginia,  where  it  is  several  hundred  feet  thick.  It  occurs 
also  in  Northern  Maine,  and  at  Gaspe  on  the  Gulf  of  St. 
Lawrence,  where  the  rock  is  partly  limestone. 

In  Great  Britain  the  Upper  Silurian  rocks  are  first  sand- 
stones and  shales,  called,  where  occurring  in  South  Wales, 
Llandovery  beds,  and  corresponding  to  the  Medina  and  Clin- 
ton groups.  Above  these  there  is  the  Wenlock  limestone 
group,  consisting  of  limestone  and  some  shale  (and  including, 
in  the  upper  portion,  the  Dudley  limestone).  These  rocks 
occur  as  surface-rocks  near  the  borders  of  Wales  and  England. 
Next  comes  the  Ludlow  group,  of  the  age  of  the  Lower  Hel- 
derberg  and  Oriskany  beds. 

In  Scandinavia  the  Gothland  limestone  is  the  equivalent 
of  the  Niagara. 

3.    Life. 

The  limestone  strata  and  most  of  the  other  beds  of  the 
Niagara  group  are  full  of  fossils ;  and  so  also  are  the  rocks  of 


96 


PALEOZOIC   TIME. 


the  Lower  Helderberg  period,  and  of  the  Wenlock  and  Ludlow 
formations  in  Great  Britain.  The  Salina  formation  is  desti- 
tute of  them. 

The  life  of  the  era  was  the  same  in  general  features  as  that 
of  the  latter  half  of  the  Lower  Silurian,  though  mostly  dif- 
ferent in  species. 

Figs.  154-166. 
154 


RADIATES :  Fig.  154,  Zaphrentis  bilateralis,  Clinton  group ;  155,  Favosites  Niagarensis, 
Niagara  group  ;  156,  Halysites  catenulata,  id.;  157,  Caryocrinus  ornatus,  id. — MOL- 
LTTSKS  :  Fig.  158,  Pentamerus  oblongus,  Clinton  gr.  ;  159,  Orthis  biloba  (x  2),  Niagara 
gr.,  and  Dudley  limestone ;  160,  Leptsena  transversalis,  id.  ;  161,  Stropliomena  rhomboida- 
lis,  id.  ;  162,  Rhynchonella  cuneata,  U.  S.  and  Great  Britain,  id.  ;  163,  Avicula  emacerata, 
Niagara  gr.  ;  164,  Cyclonema  cancellata,  Clinton  gr.  ;  165,  Platyceras  angulatura,  Niagara 
gr.  —  ARTICULATES  :  Fig.  166,  Homalonotus  delphinocephalus,  id. 

The  only  plants  yet  found  in  the  Lower  Helderberg  and 
underlying  beds  are  Algce,  or  Sea- weeds ;  but  in  the  Oriskany 


UPPER  SILURIAN.  97 

beds  of  Gaspe  are  found  remains  of  true  terrestrial  species,  re- 
lated to  the  Lycopods  or  modern  Ground-pine.  They  were 
about  as  large  as  the  common  Lycopodium  dcndroideum  of  the 
present  day.  (See  page  60.)  Similar  remains  of  plants  have 
been  found  also  in  the  Upper  Ludlow  beds  of  Great  Britain. 

In  the  Animal  Kingdom  the  sub-kingdom  of  Radiates  was 
represented  most  prominently  by  Corals  and  Crinoids ;  that 
of  Mollusks,  by  species  of  all  the  grand  divisions,  among  which 
the  Brachiopod  and  Orthoceras  tribes  were  the  most  character- 
istic, and  especially  the  Brachiopod,  whose  shells  far  outnum- 
ber those  of  all  other  Mollusks  ;  that  of  Articulates,  by  Worms, 
Ostracoids,  and  Trilobites ;  and,  before  the  close  of  the  era,  by 
the  new  form  of  Crustaceans  represented  in  Fig.  174 

1.  Radiates.  —  Fig.  154  is  a  polyp-coral  of  the  Cyathophyl- 
loid  tribe,  showing  the  radiating  plates  of  the  interior ;  Fig. 
155,  a  species  of  Favosites,  a  genus  in  which  the  corals  have 
a  columnar  structure  (somewhat  honeycomb-like,  whence  the 
name  from  the  Latin  favus,  honeycomb),  and  horizontal  parti- 
tions subdivide  the  cells  within ;  Fig.  156,  Haly sites  catenulata, 
called  chain-coral ;  Fig.  157,  a  Crinoid,  Caryocrinus  ornatus, 
the  arms  at  the  summit  broken  off;  Fig.  89,  page  57,  another 
Crinoid  of  the  family  of  Cystideans,  from  the  Niagara  group  ; 
Fig.  87,  page  57,  a  star-fish,  also  from  the  Niagara  group. 

2.  Mollusks.  —  Figs.  158  to  162,  different  Brachiopods  of 
the  Niagara  period;  Figs.  167  to  171,  other  species  charac- 
teristic of  the  Lower  Helderberg  period;  Figs.  164,  165,  Gas- 
teropods,  and  Fig.  163  a  Lamellibranch  of  the  Niagara  period. 
Fig.  172  represents  small  slender  tubular  cones,  called  Tentac- 
ulites,  which  almost  make  up  the  mass  of  some  layers  in  the 
Lower  Helderberg ;  the  form  of  one  enlarged  is  shown  in  Fig. 
173  ;  they  are  regarded  as  the  shells  of  Pteropods. 

3.  Articulates.  —  Fig.  166  is  a  reduced  figure  of  a  common 
Trilobite  of  the  Niagara  group,  a  species  of  Homalonotus,  often 
having  a  length  of  8  or  10  inches.     Fig.  174  represents  Eu~ 
rypterus  remipes,  a  species  of  a  new  family  of  Crustaceans, 
commencing  in  the  Lower  Helderberg ;  it  is  sometimes  nearly 


98 


PALEOZOIC   TIME. 


a  foot  long.  Species  of  the  same  family  occur  in  Great 
Britain  in  the  Ludlow  beds,  and  one  of  them  is  supposed, 
from  the  fragments  found,  to  have  been  6  or  8  feet  long, 
far  surpassing  any  Crustacean  now  living;  Fig.  175,  an 
Ostracoid  Crustacean,  the  Leperditia  alta,  of  unusually 
large  size  for  the  family,  modern  Ostracoids  seldom  exceed- 
ing a  twelfth  of  an  inch  in  length. 

Figs.  167-175. 

168 


MOLLTJSKS :  Figs.  167,  168,  Pentamerus  galeatus ;  169,  170,  Ehynchonella  ventricosa ; 
171,  Spirifer  macropleurus  ;  172,  Tentaculites  irregularis  ;  173,  id.  enlarged.  —  ARTICU- 
LATES :  Fig.  174,  Eurypterus  remipes,  a  small  specimen  ;  "175,  Leperditia  alta.  Species 
all  from  the  Lower  Helclerberg  group. 

4.  Vertebrates.  —  The  first  remains  of  Vertebrates  yet  dis- 
covered occur  in  the  Upper  Silurian.  They  are  of  fishes,  and 
have  been  found  in  the  Ludlow  beds  of  Great  Britain.  They 
are  teeth,  scales,  and  other  relics,  chiefly  of  shark-like  species. 
The  kinds  are  further  described  under  the  Devonian. 


4.    General  Observations. 

1.  Geography,  —  On  the  map,  page  69,  the  areas  over  which 
the  Silurian  formations  are  surface-rocks  are  distinguished  by 


UPPER  SILURIAN.  99 

being  horizontally  lined.  It  is  observed  that  they  spread 
southward  from  the  northern  Archaean  area,  and  indicate  an 
extension  in  that  direction  of  the  growing  continent. 

South  of  the  Silurian  area  commences  the  Devonian,  which 
is  vertically  lined;  and  the  limit  between  them  shows  ap- 
proximately the  course  of  the  sea-shore  at  the  close  of  the 
Silurian  age.  It  is  seen  that  more  than  half  of  New  York, 
and  nearly  all  of  Canada  and  Wisconsin,  had  by  that  time 
become  part  of  the  dry  land;  but  a  broad  bay  covered  the 
Michigan  region  to  the  northern  point  of  Lake  Michigan, 
for  here  Devonian  rocks,  and  to  some  extent  Carboniferous, 
were  afterward  formed.  The  Archaean  dry  land,  the  nucleus 
of  the  continent,  had  also  received  additions  in  a  similar 
manner  on  its  eastern  and  western  sides,  through  British 
America.* 

But,  with  all  the  increase,  the  amount  of  dry  land  in  North 
America  was  still  small.  "  Europe  is  proved  by  similar  evi- 
dence to  have  had  much  submerged  land.  The  surface  of  the 
earth  was  a  surface  of  great  waters,  with  the  continents  only 
in  embryo,  —  one  large  area  and  some  islands  representing 
that  of  North  America,  and  an  archipelago  that  of  Europe. 
The  emerged  land,  moreover,  was  most  extensive  in  the 
higher  latitudes.  The  rivers  of  a  world  so  small  in  its  lands 
must  also  have  been  small.  The  lands,  too,  according  to 
present  evidence,  had  no  green  sward  over  the  rocks,  except 
during  the  closing  part  of  the  Silurian  age. 

The  succession  of  Upper  Silurian  formations  is  as  follows  : 
1.  The  Medina  sandstone  having  at  base  the  coarse  grit  called 
Oneida  conglomerate,  occurring  of  great  thickness  along  the 
Appalachian  region,  and  reaching  north  to  Central  New  York, 

*  On  the  map  referred  to,  page  69,  lines  of  the  Silurian  and  Devonian  are 
seen  to  extend  from  the  Hudson  River  southwestward  along  the  Appalachian 
region.  But  the  outcrop  of  the  Silurian,  here  represented,  is  not  evidence 
that  there  was  a  strip  of  dry  land  along  this  region  from  the  close  of  the  Silu- 
rian era,  because  there  is  proof  that  these  Appalachian  outcrops  are  a  conse- 
quence of  the  uplift  of  the  Alleghany  Mountains,  an  event  of  much  later 
date.  (Page  151.) 


100  PALEOZOIC  TIME. 

and,  besides,  spreading  westward  beyond  the  limits  of  that 
State;  2.  The  Clinton  group  of  flags  and  shales,  having 
the  same  Appalachian  extension  and  great  thickness,  but 
spreading  on  the  north  much  farther  westward,  even  to  the 
Mississippi;  3.  The  Niagara  group,  covering  the  Appalachian 
region  deeply  with  sandstones  and  shales,  and  New  York  with 
shales  and  limestones,  and  spreading  as  a  great  limestone 
formation  through  the  larger  part  of  t!4e«Interior  region;  then 
(4)  the  limited  Salina  salt-bearing  nMrl^fces  of  New  York,  ex- 
tending west  through  Canada,  and  AVer  part  of  the  Appala- 
chian region  southwest ;  then  (5}  anwther  limestone,  but  im- 
pure, spreading  over  New  York  Stmte  and  the  Appalachian 
region,  and  also  some  of  the  Statesklvest ;  and  also  occurring 
in  the  Connecticut  Valley  anctovop  Maine  to  the  Gulf  of  St. 
Lawrence.  These  facts  teach  tuW  geographical  changes  took 
place  from  time  to  time,  in  tha^ourse  of  the  era,  corresponding 
to  these  several  changes  in  the  formations.  The  clear  conti- 
nental seas  of  the  Trenton  period  were  succeeded  by  con- 
ditions fitted  to  produce  Ij^e-^everal  arenaceous  and  argilla- 
ceous formations,  of  v^irymor  limits,  which  followed  ;  but  clear 
waters  returned  again  sN^tiieWpoch.  of  the  Niagara  group,  when 
corals,  crinoids,  and  shevtai  covered  the  bottom  of  the  conti- 
nental sea  and  made  the  Niagara  limestone  formation.  But 
these  seas  in  the  Niagara\epoch  were  less  extended  than  those 
of  the  Trenton ;  for  the  4PPalacnian  region,  instead  of  being 
part  of  the  pure  sea  and  making  limestones,  was  receiving 
great  depositions  of  sand  and  clay,  as  if  it  wrere  at  the  time 
a  broad  reef,  or  bank,  bordering  the  Atlantic  Ocean. 

The  Niagara  epoch  of  limestone-making  was  followed  by 
the  Salina  or  saliferous  period.  Since  the  beds  are  (1)  clays 
and  clayey  sands,  (2)  are  almost  wholly  without  fossils,  and 
(3)  afford  salt,  it  may  be  inferred  that  Central  New  York  was 
at  the  time  a  great  salt  marsh,  mostly  shut  off  from  the  sea. 
Over  such  an  area  the  waters  would  at  times  have  become  too 
salt  to  support  life,  owing  to  partial  evaporation  under  the 
hot  sun,  and  too  fresh  at  other  times,  from  the  rains.  More- 


UPPER  SILURIAN.  101 

over,  muddy  deposits  would  have  been  formed ;  for  they  are 
now  common  in  salt  marshes  wherever  there  is,  as  there  was 
then,  no  covering  of  vegetation,  and  the  salt  waters  would 
naturally  have  yielded  salt  on  evaporation  in  the  drier  sea- 
sons. Through  an  occasional  ingress  of  the  sea,  the  salt 
waters  might  have  been  resupplied  for  further  evaporation. 

There  is  direct  testimony  as  to  the  condition  of  the  land 
and  shallowness  of  the  waters  in  the  regions  where  many 
of  the  rocks  were  in  progress;  for  ripple-marks  and  mud- 
cracks  are  common  in  some  layers,  and  are  positive  evidence 
that  the  sands  and  earth  that  are  now  the  solid  rock  were 
then  the  loose  sands  of  beaches,  sand-flats,  or  sea-bottoms,  or 
the  mud  of  a  salt  marsh.  Such  little  markings,  therefore, 
remove  all  doubt  as  to  the-  condition  of  Central  New  York  in 
the  Salina  period. 

Similar  markings  indicate^  ;also,  the  precise  condition  of 
the  region  of  the  Medina  sandstone,  showing  that  there  were 
sand-flats,  sea-beaches,  and  muddy  bottoms  open  to  the  in- 
flowing sea.  Where  the  rt&Hpf&ftfc  were  made  (Fig.  19,  page 
33)  the  sands  of  the  spot  were  t^se  o£  a  gently  sloping  flat 
or  beach ;  the  waters  swept  lighflyyver  the  sands,  dropping 
here  and  there  a  stray  shell  (asjfhe  Lingula  cuneata}  or  a 
pebble,  which  became  partly  buried;  and  then,  as  they 
retreated,  they  made  a  tiny  plunge  over  the  little  obstacle 
and  furrowed  out  the  loose  sand  below  it.  The  fineness  of 
the  sand,  lightness  of  the  shells,  and  smallness  of  the  furrows 
are  proof  that  the  movements  were  light. 

The  great  thickness  of  the  several  formations  of  the  Upper 
Silurian  along  the  Appalachian  region  leads  to  many  inter- 
esting conclusions.  It  has  been  stated  (page  91)  that  the 
Appalachian  formations  of  the  earlier  Silurian  were  equally 
remarkable  for  their  great  thickness.  The  Appalachian  re- 
gion, from  the  Primordial  era  onward,  was,  hence,  in  strong 
contrast  with  the  Interior  Continental  region,  where  the 
series  of  cotemporaneous  beds  are  hardly  one  tenth  as  thick. 
Taking  this  into  connection  with  another  fact,  that  very 


102  PALEOZOIC  TIME. 

many  of  the  strata  among  the  thousands  of  feet  of  Silurian 
formations  in  the  Appalachian  region  contain  those  evidences 
of  shallow  water  and  mud-flat  or  sand-flat  origin  above  ex- 
plained, there  is  full  proof  that  in  the  Silurian  era  the  region 
was  for  the  most  part,  as  already  suggested,  a  vast  sand-reef, 
ever  increasing  by  new  accumulations  under  the  action  of  the 
waves  and  currents  of  the  ocean.  It  was  much  of  the  time  a 
great  barrier-reef  lying  between  the  open  ocean  and  the  Inte- 
rior Continental  sea ;  and  under  its  lee,  this  inner  sea,  opening 
southward  through  the  area  of  the  Mexican  Gulf,  was  often 
in  the  best  condition  for  the  growth  of  the  Shells,  Corals,  and 
Crinoids  of  which  the  great  limestones  were  made. 

While  the  Appalachian  region  was  alike  in  its  general  con- 
dition through  the  earlier  and  later  Silurian,  the  limits  of  the 
formations  in  progress  during  these  two  eras  were  somewhat 
different,  as  explained  on  page  91.  The  part  of  the  Appala- 
chian region  which  participated,  during  the  Upper  Silurian 
era,  in  the  great  changes  connected  with  the  formation  of 
rocks,  extended  northward  from  Pennsylvania  into  New  York, 
and  not  along  the  Green  Mountains ;  the  rocks  in  the  State 
of  New  York  have  great  thickness  for  some  distance  beyond 
the  Pennsylvania  border,  but  thin  out  about  the  centre. 

2.  Life.  —  In  the  Upper  Silurian  the  highest  species  of  the 
seas  and  of  the  world  continued  for  a  while  to  be  Mollusks, 
of  the  order  of  Cephalopods.  But  before  its  close  there  were 
fishes  in  the  waters,  and  Vertebrates  ever  afterward  existed  as 
the  highest  species.  Corals  and  Crinoids  were  the  only  kinds 
of  life  that  had  the  semblance  of  flowers.  These  flower-ani- 
mals foreshadowed  the  flowers  of  the  vegetable  kingdom  for 
ages  before  any  of  the  latter  existed.  The  little  Lycopods  of 
the  later  part  of  the  Upper  Silurian  were  flowerless  plants, 
like  Ferns. 

Up  to  1872,  over  10,000  species  of  Silurian  animals  — 
ranging  from  Sponges  to  Fishes  —  had  been  made  known 
through  the  study  of  fossils. 


DEVONIAN  AGE.  103 


II.    AGE    OF    PISHES,    or    DEVONIAN    AGE. 
I.    Subdivisions. 

The  Devonian  formation  was  so  named  by  Sedgwick  and 
Murchison,  from  Devonshire,  England,  where  it  occurs. 

The  Age  may  be  divided  into  two  eras,  —  an  earlier  and  a 
later,  or  that  of  the  lower  and  that  of  the  upper  formations. 
The  Lower  Devonian  includes  the  CORNIFEROUS  period;  the 
Upper  Devonian,  the  HAMILTON,  CHEMUNG,  and  CATSKILL 
periods. 

2.    Rocks:   Kinds  and  Distribution. 

1.  Earlier  and  Later  Eras. — The  Lower  Devonian  is  remark- 
able for  a  great  limestone  formation,  which  spread  from  New 
York  over  a  large  part  of  the  Interior  region,  and  nearly 
equalled  the  Trenton  in  extent;  while  the  Upper  includes 
very  little   limestone,  the   rocks   being   mainly   sandstones, 
shales,  and  conglomerates. 

2.  Comiferous  Period.  —  The  lowest  rocks  of  this  period  are 
fragmental  beds,  called  the  Cauda-Galli  grit  and  the  Scho- 
harie  grit,  having  their  distribution  along  the  Appalachian 
region,  commencing  in  Central  and  Eastern  New  York  and 
extending  southwestward. 

Next  follows  the  great  Comiferous  limestone,  the  lower 
part  of  which  is  sometimes  called  the  Onondaga  limestone, 
and  the  whole  often  the  Upper  Helderlerg  group.  It  stretches 
from  Eastern  New  York  westward  to  the  States  beyond  the 
Mississippi. 

The  name  Comiferous  (derived  from  the  Latin  cornu,  horn) 
was  given  it  by  Eaton,  from  its  frequently  containing  a  kind 
of  flint  called  hornstone.  This  hornstone  differs  from  true 
flint  in  being  less  tough,  or  more  splintery  in  fracture,  though 
it  is  like  it  in  hardness  and  in  consisting  wholly  of  silica. 

The  limestone  is  in  many  places  literally  an  ancient  coral 
reef.  It  contains  corals  in  vast  numbers  and  of  great  variety ; 


104  PALEOZOIC  TIME. 

and  in  some  places,  as  at  the  Falls  on  the  Ohio,  near  Louis- 
ville, Kentucky,  the  resemblance  to  a  modern  reef  is  perfect. 
Some  of  the  coral  masses  at  that  place  are  5  or  6  feet  in  di- 
ameter; and  single  polyps  of  the  Cyathophylloid  corals  had 
in  some  species  a  diameter  of  2  and  3  inches,  and  in  one,  of  6 
or  7  inches. 

The  same  reef-rock  occurs  near  Lake  Memphremagog  on 
the  borders  of  Yermont  and  Canada,  and  also  at  Littleton, 
New  Hampshire;  but  the  corals  have  in  these  places  been 
partly  obliterated  by  metamorphism. 

3.  Hamilton  Period.  —  The  Hamilton  formation  consists  in 
New  York  of  sandstones  and  shales,  with  a  few  thin  layers  of 
limestone.     It  consists  of  three  parts,  corresponding  to  three 
epochs :  the  lower  part  is  called  the  Marcellus  shale ;  the 
middle,  the  Hamilton  beds ;  and  the  upper,  the  Genesee  shale. 
It  has  its  greatest  thickness  along  the  Appalachians.     From 
New  York  it  spreads  westward,  where  it  is  in  part  calcareous, 
and  forms  the  upper  part  of  the  "cliff"  limestone.     It  in- 
cludes a  stratum  of  Hack  shale  (supposed  to  be  of  the  epoch 
of  the  Genesee  shale),  100  to  350  feet  thick,  which  yields  in 
some  places  15  to  20  per  cent  of  mineral  oil.     The  formation 
occurs  also  in  Eastern  Maine,  New  Brunswick,  and  at  Gaspe, 
on  the  Gulf  of  St.  Lawrence. 

The  Hamilton  beds  afford  an  excellent  flagging-stone  in 
Central  New  York,  and  on  the  Hudson  River,  near  Kingston, 
Saugerties,  Coxsackie,  and  elsewhere,  which  is  extensively 
quarried  and  exported  to  other  States. 

4.  Chemung  Period.  —  The  Chemung  beds  are  mainly  sand- 
stones, or  shaly  sandstones,  with  some  conglomerate.     They 
spread  over  a  large  part  of  Southern  and  Western  New  York, 
having  great  thickness  in  the  Catskill  Mountains.     A  shale 
of  the  period  in  Northern  Ohio  is  called  the  Erie  shale. 

The  formation  along  the  Appalachians  is  5,000  feet  thick. 
It  thins  out  to  the  west  of  New  York,  in  Ohio,  and  Michigan. 

In  the  following  section,  taken  on  a  north-and-south  line 
south  of  Lake  Ontario,  No.  6  represents  the  beds  of  the 


DEVONIAN   AGE.  105 

Salina  period  ;  overlaid  by  7,  the  Lower  Helderberg  lime- 
stone ;  9,  the  Corniferous,  or  Upper  Helderberg  limestone  ; 
10,  a,  b,  c,  the  Hamilton  beds  ;  and  11,  the  Chemung  group. 


Fig.  176. 


t>  7  9  10  a 

Section  of  Devonian  formations  south  of  Lake  Ontario. 

5.  Catskill  Period,  —  The  rocks  are  sandstones,  shaly  sand- 
stones, and  shales ;  they  occur  in  Eastern  New  York,  and  are 
2,000  to  3,000  feet  thick  in  the  Catskill  Mountains.  They 
also  extend  southwestward  along  the  Appalachians,  being 
5,000  to  6,000  feet  thick  in  Pennsylvania. 

In  Great  Britain  the  Devonian  rocks  include  the  Old  Red 
Sandstone,  the  prevailing  rock  of  the  age  in  Wales  and  Scot- 
land. The  thickness  in  some  places  is  8,000  to  10,000  feet. 
This  formation,  besides  sandstone,  includes  marlytes  of  red  and 
other  colors,  and  some  limestone.  The  distribution  in  Great 
Britain  is  shown  on  the  map,  page  118.  In  Germany,  in  the 
Rhenish  provinces,  there  is  a  coral  limestone  very  similar  to 
that  of  North  America. 

3.    Life. 
1.    General  Characteristics. 

The  Devonian  of  North  America  was  characterized  by 
forests  and  an  abundance  of  insects  over  the  land,  and 
by  fishes  of  many  kinds  in  the  waters. 

2.    Plants. 

Figs.  177-179  represent  portions  of  some  of  the  plants. 
Fig.  179  is  a  fragment  of  a  Fern,  and  Figs.  177,  178,  portions 
of  the  trees,  of  the  age.  The  scars  or  prominences  over  the 
surface  are  the  bases  of  the  fallen  leaves :  a  dried  branch  of 
a  Norway  spruce,  stripped  of  its  leaves,  looks  closely  like 
Fig.  178.  By  referring  to  page  60,  it  will  there  be  seen  that 

5* 


106 


PALEOZOIC   TIME. 


among  the  Cryptogams  there  is  one  order,  the  highest,  or 
that  of  Acrogens,  in  which  the  plants  have  upward  growth 


PLANTS.  —  Fig.  177,  Lepidodendron  primaevum,  from  the  Hamilton  group ;  178,  Sigillaria 
Hallii,  ibid. ;  179,  Noeggerathia  Halliana,  from  the  Chemung  group. 

like  ordinary  trees,  and  the  tissues  are  partly  vascular :  it  is 
the  one  containing  the  Ferns,  Lycopods,  and  Equiseta  or  Horse- 
tails. The  most  ancient  of  land  plants  belong,  to  a  great  ex- 
tent, to  this  order,  —  the  highest  of  Cryptogams,  and  were  of 
the  three  kinds  just  mentioned.  Another  portion  are  related 
to  the  lowest  order  of  flower-bearing  plants  or  Phenogams, 
called  Gymnosperms  (see  page  62). 

The  groups  represented  under  these  divisions  are  the  fol- 
lowing :  — 

I.    Flowerless   Plants,  or  Cryptogams,   Order  of 
Acrogens. 

1.  Fern  Tribe.  —  The  species  have  a  general  resemblance  to 
the  ferns  or  brakes  of  the  present  time. 

2.  Lycopods,  or  plants  related  to  the  Ground-Pine.  —  The 
existing  plants  of  this  tribe  are  slender  species,  seldom  over  4 
or  5  feet  high :  some  of  the  ancient  kinds  were  of  the  size  of 


DEVONIAN  AGE.  107 

forest-trees.  These  ancient  species  belong  mostly  to  the  Lepi- 
dodendron  family,  in  which  the  scars  are  contiguous  and  are 
arranged  in  quincunx  order,  that  is,  alternate  in  adjoining 
rows,  as  shown  in  Fig.  177.  The  name  Lepidodendron  is 
from  the  Greek  A.67T69,  scale,  and  SevSpov,  tree,  and  alludes  to 
the  scar-covered  trunk,  which  looks  something  in  surface  like 
a  scale-covered  reptile.  The  Ground-Pine  of  modern  woods, 
although  flowerless  like  the  fern,  has  leaves  very  similar  to 
those  of  the  Spruce  or  Cedar  (Conifers) ;  and  this  type  of 
plants  is  intermediate  in  some  respects  between  the  Aero- 
gens  and  Gymnosperms  (Conifers). 

The  Sigillarids,  another  family  in  this  tribe,  included  trees 
of  moderate  height,  with  stout,  sparingly  branched  trunks, 
bearing  long  linear  leaves  much  like  those  of  the  Lepidoden- 
drids  ;  but  the  scars  on  the  exterior  are  mostly  in  parallel 
vertical  lines,  as  in  Fig.  178,  and  Fig.  222,  page  125,  and  not 
in  quincunx  order,  like  those  of  the  Lepidodendra.  The  name 
is  from  the  Latin  sigillum,  a  seal,  in  allusion  to  the  scars. 

3.  Equisetum,  or  Horse-tail  Tribe,  —  The  Equiseta  of  mod- 
era  wet  woods  are  slender,  hollow,  jointed  rushes,  called 
sometimes  scouring -rushes.  They  often  have  a  circle  of  slen- 
der leaf-like  appendages  at  each  joint.  The  Calamites  or  Tree- 
rushes,  which  are  referred  to  this  tribe,  are  peculiar  to  the 
ancient  world,  none  having  existed  since  the  Mesozoic.  They 
had  jointed  striated  stems  like  the  Equiseta,  and  otherwise 
resembled  them.  But  they  were  often  a  score  of  feet  or  more 
in  height,  and  over  6  inches  in  diameter.  Some  of  them  had 
hollow  stems  like  the  Equiseta ;  others  had  the  interior  of  the 
stems  partially  woody,  and  these  were  intermediate  in  some 
respects  between  the  Equiseta  and  the  Gymnosperms.  Fig. 
225,  page  125,  represents  a  portion  of  one  of  these  plants. 

II.  Flowering  Plants,  or  Phenogams,  of  the  Order 
of  Gymnosperms. 

Conifers.  —  The  species  are  related  to  the  common  Pines 
and  Spruces,  or  more  nearly  to  the  Araucanian  Pines  of  Aus- 


108  PALEOZOIC   TIME. 

tralia  and  South  America.  The  fossils  are  merely  portions  of 
the  trunk  or  branches. 

Conifers,  Ferns,  and  Lepidodendrids  have  also  been  reported 
from  some  of  the  Devonian  beds  of  Britain  and  Europe. 

The  hornstone,  which  is  massive  quartz,  or  silica,  develops, 
under  the  microscope,  the  fact  that  it  was  probably  made 
from  the  siliceous  remains  of  plants  and  animals.  Figs.  180 
to  194  represent  some  of  the  species  which  have  been  detected 
by  Dr.  M.  C.  White  in  specimens  from  New  York  and  else- 
where. Figs.  180  to  186  are  microscopic  plants,  related  to 


Microscopic  Organisms  from  the  Hornstone. 

the  Desmids ;  Fig.  187  is  another  kind,  called  a  Diatom,  a 
kind  which  forms  siliceous  shells,  and  which  is  probably  one 
of  the  sources  of  the  silica  of  which  the  hornstone  was  made. 
(See,  on  Diatoms  and  Desmids,  page  61.)  Figs.  188,  189  are 
spicules  of  Sponges,  also  siliceous,  and  another  of  the  sources 
of  the  silica.  Figs.  190-192  are  probably  also  sponge-spi- 
cules.  Figs.  193,  194  are  fragments  of  the  teeth  of  some 
Gasteropod  Mollusk.  The  last  is  from  a  hornstone  of  the 
Trenton  period  which  was  found  to  afford  the  same  evidences 
of  organic  origin. 

3.  Animals. 

The  early  Devonian  was  the  coral  period  of  the  ancient 
world.  In  no  age  before  or  since,  not  even  the  present,  have 
coral  reefs  of  greater  extent  been  formed. 

Among  Mollusks,  Brachiopods  were  still  the  prevailing 
kinds,  though  ordinary  Bivalves  or  Lamellibranchs,  and 


DEVONIAN   AGE. 


109 


Univalves  or  Gasteropoda,  were  more  abundant  than  in 
the  Silurian.  A  new  type  of  Cephalopods  commenced  in  the 
Middle  Devonian.  Hitherto,  the  partitions  or  septa  in  the 
shells,  straight  or  coiled,  were  flat  or  simply  concave;  but 
in  the  new  genus  Goniatites  the  margin  of  the  plate  has  one 
or  more  deep  flexures,  one  of  the  flexures  or  pockets  being  at 
the  middle  of  the  back  of  the  shell.  The  name  is  from  the 
Greek  yovv,  knee  or  angle.  Fig.  205  (page  110)  represents 
one  of  the  species,  and  Fig.  205  a  shows  some  of  the  flexures 
along  the  back  of  the  shell. 

Among  Articulates  there  were  Worms  and  Crustaceans,  as 
in  earlier  time,  and  the  most  common  Crustaceans  were  Trilo- 
bites.  Besides  these  there  were  the  first  of  Insects,  the  wings 
of  some  species  having  been  reported  from  the  Devonian  of 
New  Brunswick. 


Figs.  195-199. 
196  a  vrflK  .     197 


RADIATES.  — Fig.  195,  Zaphrentis  Rafinesquii ;  196,  196  a,  Cyathophyllum  rugosuin ; 
197,  Syringopora  Maclurii ;  198,  Aulopora  cornuta ;  199,  Favosites  Goldfussi :  all  of  the 
Corniferous  period. 

L  Radiates.  —  Fig.  195,  one  of  the  Cyathophylloid  corals, 
Zaphrentis  Rafinesquii  ;  Fig.  196,  another,  Cyathophyllum  ru- 
gosum,  both  from  the  Falls  of  the  Ohio,  and  the  latter  form- 
ing very  large  masses.  Fig.  196  a  is  a  top  view  of  the  cells 
in  Fig.  196.  Fig.  199,  a  Favosites  from  the  same  locality, 
showing  well  the  columnar  structure  characterizing  the  genus : 


110 


PALEOZOIC   TIME. 


the  species  F.  Goldfussi  occurs  both  in  America  and  Europe. 
Figs.  197  and  198  are  small  corals  from  Canada  West. 

2.  Mollusks.  —  Figs.    200    to   202,   Brachiopods   from   the 
Hamilton  beds;   Figs.   203,  204,  Lamellibranchs,  from   the 


Pigs.  200-206. 


200 


203 


MOLLUSKS:  Fig.  200,  Atrypa  aspera ;  201,  Spirifer  mucronatus;  202,  Chonetes  setigera; 
203,  Grammysia  bisulcata;  204,  Microdon  bellistriatus ;  205,  205  a,  Goniatites  Marcel- 
lensis  :  all  from  the  Hamilton  group.  —  ARTICULATES  :  Fig.  206,  Phacops  bufo,  from 
the  Hamilton  group. 

same ;  Fig.  205,  the  Cephalopod,  Goniatites  Marcellensis, 
ibid. ;  Fig.  205  a,  a  view  of  the  back,  showing  the  flexures 
in  the  partitions,  this  species  having  but  one  flexure  or 
pocket. 

3.  Articulates.  — Fig.  206,  the  Trilobite,  Phacops  lufo, 
one  of  the  common  species  of  the  Hamilton.  The  earliest 
remains  of  Insects  yet  discovered  have  been  found  in  beds 


DEVONIAN   AGE. 


Ill 


Fig.  207. 


supposed  to  be  of  the  Hamilton  era,  at  St.  John's,  New 
Brunswick.  A  wing  of  a  gigantic  species  of  May-fly  is 
represented  in  Fig.  207. 

4.  Vertebrates,  —  The  fishes 
of  the  Devonian  belong  to 
three  orders  :  1.  the  Selachians, 
or  Sharks;  2.  the  Ganoids;  and 
3.  the  Placoderms.  The  Placo- 
derms  are  represented  in  Figs. 
208,  209.  The  name,  from  the 
Greek,  alludes  to  the  plates 
that  cover  the  body  much  like  those  of  a  turtle. 

Some  of  the  Ganoids  are  shown  in  Figs.  210-215.     The 

Figs.  208,  209. 


Platephemera  antiqua. 


VERTEBRATES.  —  Fig.  208,  Pterichthys  Milled  (X  |) ;  209,  Coccosteus  decipiens  (X  i)- 

Ganoids  are  related  to  the  Gar-pike  of  some  modern  lakes 
and  rivers,  a  kind  of  fish  now  rarely  met  with.  They  have 
bony,  shining  scales,  and  to  this  the  name,  from  701*09,  shin- 
ing, alludes.  As  remarked  by  Agassiz,  they  have  several 


112 


PALEOZOIC   TIME. 


characters  that  ally  them  to  Eeptiles ;  that  is,  (1)  they  have 
the  power  of  moving  the  head  at  the  articulation  between  the 
head  and  the  body,  the  articulation  being  made  by  means  of 
a  convex  and  concave  surface ;  (2)  the  air-bladder,  which  an- 
swers to  the  lung  of  higher  animals,  has  a  cellular  or  lung- 


Pigs.  210-215. 
210 


GANOIDS.  —  Fig.  210,  Cephalaspis  Lyellii  (x  f )  ;  211,  212,  scales  of  same ;  213,  Holopty- 
chins  (X  i);  214,  scale  of  same;  215,  Dipterus  macro!  epidotus  (X  ^);  215  a,  scale  of 
same. 

like  structure,  thus  approximating  the  species  to  air-breathers; 
(3)  the  teeth  have  in  general  a  structure  like  that  of  the  early 
Amphibians.  These  early  species  had  the  tail  vertebrated  (or 
heterocercal),  as  illustrated  in  Fig.  215.  Fig.  210  represents 
the  Cephalaspis,  having  a  flat  and  broad  plate-covered  head, 
with  rhombic  scales  over  the  body :  Fig.  212  shows  the 


DEVONIAN  AGE.  113 

form  of  some  of  the  scales.  Fig.  215  is  a  species  of  Dip- 
terus,  covered  with  rhombic  scales,  put  on,  as  in  the  pre- 
ceding, much  as  tiles  are  arranged  on  a  roof:  Fig.  215  a 
is  one  of  the  scales,  natural  size.  Fig.  213  represents  another 
type  of  Ganoids,  having  the  scales  rounded  (as  shown  in  Fig. 
214)  and  set  on  more  like  shingles;  it  is  a  Holoptychius. 

These  figures  are  all  much  reduced.  Scales  of  a  Holopty- 
chius have  been  found  in  Chemung  beds  which  were  over  an 
inch  and  a  half  broad,  indicating  the  existence  of  fishes  of 
great  size. 

The  Selachians,  or  species  of  the  shark  tribe,  belong  in  part 
to  the  family  of  Cestracionts  (page  53),  or  that  in  which  the 
mouth  has  a  pavement  of  broad  bony  pieces  for  grinding. 
The  food  in  the  seas  for  these  carnivorous  Fishes  consisted 

Fig.  216. 


Fin-spine  of  a  Shark  ( x  |). 

mainly  of  shell-fish  and  mail-clad  Ganoids;  and  grinders 
were,  therefore,  well  suited  for  the  times.  Many  of  these 
Cestraciont  sharks  were  of  a  very  large  size.  Fig.  216  repre- 
sents a  fin-spine  of  one,  drawn  two  thirds  its  actual  size, 
found  in  the  Corniferous  beds  of  the  State  of  New  York. 

4.  General  Observations. 

1.  Geography.  —  During  the  Silurian,  there  had  been  a  grad- 
ual gain  of  dry  land  on  the  north,  extending  the  Archaean 
continent  (page  73)  southward.  This  gain  continued  through 
the  Devonian,  so  that  the  formations  of  the  next  age,  the  Car- 
boniferous, extend  only  a  short  distance  north  of  the  southern 
boundary  of  New  York.  The  sea-shore  was  thus  being  set 
farther  and  farther  southward  with  the  progressing  periods. 

The  formations  have  their  greatest  thickness  along  the  Ap- 
palachian region,  as  in  the  Silurian  age.  And  both  this-  fact 


114  PALEOZOIC   TIME. 

and  their  successions  lead  to  similar  general  conclusions  to 
those  stated  on  page  102. 

2.  Life.  —  The  great  feature  of  the  Devonian  age  is  the  oc- 
currence of  forests  of  Acrogens  and  Conifers;  of  Insects, 
among  terrestrial  Articulates ;  and  of  great  Sharks  and  Gars  in 
the  seas,  as  representatives  of  Vertebrates.  No  Mosses  appear 
to  have  existed  as  intermediate  species  between  Sea-weeds 
and  the  earliest  Ferns,  Lycopods  and  Pines. 

With  regard  to  Fishes,  the  earliest  species  belong  to  the 
two  high  groups  of  the  class,  —  the  Sharks  and  the  Ganoids; 
the  Ganoids  being  a  type  that  is  partly  Eeptilian.  The  rocks 
have  afforded  no  evidence  of  any  links  between  the  Mollusk, 
Worm,  or  Trilobite  and  these  fishes. 

III.  CARBONIFEROUS  AGE,  or  AGE  OF  COAL 
PLANTS. 

I.  General  Characteristics:  Subdivisions. 

The  Carboniferous  age  was  remarkable,  in  general,  for  — 

1.  A  low  elevation  of  the  continents  above  the  sea-level 
through  long  eras  alternating  with  small  submergences  of  the 
same. 

2.  Extensive  marshy  or  fresh- water  areas  over  large  por- 
tions of  these  low  continents. 

3.  Luxuriant  vegetation,  covering  the  land  with  forests  and 
jungles. 

4.  Scorpions,  true   Spiders,  Centipedes,  Insects,  over  the 
land,  and  Amphibians  and  other  Eeptiles  over  the  marshes 
and  in  the  seas. 

But,  while  having  these  as  its  main  characteristics,  it  was 
not  an  age  of  continued  verdure.  There  was,  first,  a  long 
period  —  the  Subcarboniferous  —  in  which  the  land  was 
largely  beneath  the  sea ;  for  limestone,  full  of  marine  fossils, 
is  the  prevailing  rock,  and  there  are  but  few,  and  mostly  thin 
coal-beds  in  the  sandstones  and  shales.  This  period  was  fol- 
lowed by  the  Carboniferous,  or  that  of  the  true  Coal-measures. 


CARBONIFEROUS  AGE.  115 

Yet  even  in  this  middle  period  of  the  age  there  were  alterna- 
tions of  submerged  with  emerged  continents,  long  eras  of  dry 
and  marshy  lands  luxuriantly  overgrown  with  shrubbery  and 
forest-trees  intervening  between  other  long  eras  of  great  bar- 
ren continental  seas.  Then  there  was  a  closing  period,  —  the 
Permian,  —  in  which  the  ocean  prevailed  again,  though  with 
contracted  limits ;  for  the  rocks  are  mainly  of  marine  origin. 

The  Carboniferous  period  and  age  were  so  named  from  the 
fact  that  the  great  coal-beds  of  the  world  originated  mainly 
during  their  progress.  The  term  Permian  was  given  to  the 
rocks  of  the  third  period  by  Murchison,  De  Yerneuil,  and 
Keyserling,  from  a  region  of  Permian  rocks  in  Eussia,  the  an- 
cient kingdom  of  Permia,  now  divided  into  the  governments 
of  Perm,  Yiatka,  Kasan,  Orenberg,  etc. 

2.  Distribution  of  Carboniferous  Rocks. 

The  Carboniferous  areas  on  the  map  of  the  United  States, 
page  69,  are  the  dark  areas ;  the  black  cross-lined  with  white 
being  the  Subcarboniferous  ;  the  pure  black,  the  Carboniferous  ; 
the  black  dotted  with  white,  the  Permian.  The  last  occur 
only  west  of  the  Mississippi. 

The  following  are  the  positions  of  the  several  great  coal 
areas  in  North  America  :  — 

1.  EASTERN  BORDER  EEGION.  —  1.  The  Rhode  Island  area, 
extending  from  Newport   in   Ehode  Island  northward  into 
Massachusetts. 

2.  The  Nova  Scotia  and  New  Brunswick  area. 

II.  ALLEGHANY  and  INTERIOR  EEGIONS.  —  1.  The  great  Al- 
leghany  area,  extending  from  the  southern  borders  of  New 
York  and  Ohio  southwestward  to  Alabama,  covering  the 
larger  part  of  Pennsylvania,  half  of  Ohio,  part  of  Kentucky 
and  Tennessee,  and  a  portion  of  Alabama.  To  the  northeast, 
in  Pennsylvania,  this  coal-field  is  much  broken  into  patches, 
as  shown  in  the  accompanying  map  of  a  part  of  the  State,  the 
black  areas  being  those  of  the  coal-district. 

2.  The  Michigan  area,  covering  the  central  part  of  the 
State  of  Michigan. 


116 


PALEOZOIC   TIME. 


3.  The  Illinois  or  Eastern  Interior  area,  covering  much  of 
Illinois,  and  part  of  Indiana  and  Kentucky. 

4.  The  Missouri,  or  Western  Interior,  covering  part  of  Iowa, 
Minnesota,  Missouri,  Kansas,  Arkansas,  and  Northern  Texas. 


5.  Besides  these,  there  is  a  barren  Carboniferous  region 
about  the  slopes  and  summits  of  the  Kocky  Mountains,  as 
around  the  Great  Salt  Lake  in  Utah,  and  also  in  California,  — 
the  workable  coal-beds  of  the  Eocky  Mountain  region  being 
Cretaceous  or  Tertiary. 


CARBONIFEROUS  AGE.  117 

III.  ARCTIC  KEGION.  —  On  Melville  Island,  and  other  isl- 
ands between  Grinnell  Land  and  Banks  Land,  mostly  north 
of  latitude  70°,  and  on  Spitzbergen  and  Bear  Island  north  of 
Siberia. 

The  areas  of  the  coal-measures  in  North  America  have  been 
estimated  as  follows : 

1.  Rhode  Island 500  square  miles. 

2.  Nova  Scotia  and  New  Brunswick     .  18,000        "         " 

3.  Alleghany     .         .         ;         .         .         .  60,000         "         " 

4.  Michigan.         .         .        .        .         .  5,000        "        u 

5.  Illinois  and  Missouri    .        .        .        .  120,000        "        " 

But  of  these,  the  workable  portion  probably  does  not  exceed 
120,000  square  miles. 

Carboniferous  strata  occur  also  in  Great  Britain  and  various 
parts  of  Europe.  The  beds  in  England  are  distributed  over 
an  area  between  South  Wales  on  the  west  and  the  Newcastle 
basin  on  the  northeast  coast  (as  shown  by  the  black  areas  on 
the  following  map),  the  most  important  for  coal  being  the 
South  Wales  region ;  the  Lancashire  district,  bordering  on 
Manchester  and  Liverpool;  the  Yorkshire,  about  Leeds  and 
Sheffield ;  and  the  Newcastle.  In  South  Wales  the  thickness 
of  the  coal-measures  is  7,000  to  12,000  feet,  with  more  than 
100  coal-beds,  70  of  which  are  worked. 

Scotland  has  some  small  areas  between  the  Grampian 
range  on  the  north  and  the  Lammermuirs  on  the  south ;  and 
Ireland,  several  coal-regions  of  large  extent,  as  at  Ulster,  Con- 
naught,  Leinster  (Kilkenny)  and  Munster. 

The  coal-fields  of  Europe  which  are  most  worked  are  the 
Belgian,  bordering  on  and  passing  into  France.  Germany 
contains  only  small  coal-bearing  areas ;  and  Eussia  in  Europe 
still  less,  although  the  Subcarboniferous  and  Permian  rocks 
cover  large  portions  of  the  surface. 

The  area  of  the  coal-measures  in  Great  Britain  and  Ireland 
is  about  12,000  square  miles;  in  Spain,  4,000;  in  France, 
2,000;  Belgium,  518. 

Valuable  coal-beds  are  not  found  in  any  rocks  older  than 


118 


PALEOZOIC   TIME. 


those  of  the  Carboniferous  age,  although  Wack  carbonaceous 
shales  are  not  uncommon  even  in  the  Lower  Silurian.  They 
occur,  however,  in  different  Mesozoic  formations,  and  also 

Fig.  218. 


Fig.  218,  Geological  Map  of  England.  The  areas  lined  horizontally  and  numbered  1  are 
Silurian.  Those  lined  vertically  (2),  Devonian.  Those  cross-lined  (3),  Subcarboniferous. 
Carboniferous  (4),  black.  Permian  (5).  Those  lined  obliquely  from  right  to  left,  Triassic 
(6),  Lias  (7  a),  Oolite  (7  b),  Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from  left  to 
right  (10,  11),  Tertiary.  A  is  London,  B,  Liverpool,  C,  Manchester,  D,  Newcastle. 


CARBONIFEKOUS   AGE.  119 

occasionally  in  the  Cenozoic,  but  not  of  the  extent  which 
they  have  in  the  Carboniferous  formations. 

3.  Kinds  of  Rocks. 

1.  Subcarboniferous  Period.  —  The  Subcarboniferous  strata 
in  the  Interior  Continental  region  are  mainly  limestone ;  and, 
as  the  limestone  abounds  in  many  places  in  Crinoidal  re- 
mains, the  rock  is  often  called  the  Crinoidal  limestone.     In 
the  Appalachian  region,  in  Middle  and  Southern  Virginia,  the 
rock  is  also  limestone,  and  has  great  thickness ;  but  in  North- 
ern Virginia  and  Pennsylvania  it  is  mostly  a  sandstone  or 
conglomerate  overlaid  by  a  shaly  or  clayey  sandstone  and 
marlytes  of  reddish  and  other  colors,  —  the  whole  having  a 
maximum  thickness  of  5,000  to  6,000  feet,     In  the  Eastern 
border  region,  in  Nova  Scotia,  the  rocks  are  mostly  reddish 
sandstone  and  marlyte,  with  some  limestone,  —  the  estimated 
thickness  6,000  feet. 

The  prevailing  rock  in  Great  Britain  and  Europe  is  a  lime- 
stone, called  there  the  Mountain  limestone. 

2.  Carboniferous  Period.  —  7.  Rocks  of  the  Coal-formation.  - 
The  rocks  of  the  Carboniferous  period  —  that  is,  those  of  the 
Coal-measures  —  are    sandstones,  shales,  conglomerates,  and 
occasionally  limestones ;  and  they  are  so  similar  to  the  rocks 
of  the  Devonian  and  Silurian  ages  that  they  cannot  be  distin- 
guished except  by  the  fossils.     They  occur  in  various  alter- 
nations, with  an  occasional  bed  of  coal  between  them.     The 
coal-beds,  taken  together,  make  up  not  more  than  one  fiftieth 
of  the  whole  thickness ;  that  is,  there  are  50  feet  or  more  of 
barren  rock  to  1  foot  of  coal.     The  maximum  thickness  in 
Pennsylvania  is  4,000  feet;  in  Nova  Scotia,  13,000  feet. 

The  following  is  an  example  of  the  alternations  :  — 

1.  Sandstone  and  conglomerate  beds    .       ,.         .         .        .  120    feet. 

2.  COAL ,-    ,  6      " 

3.  Fine-grained  shaly  sandstone  .         .         .                  .         .  50      " 

4.  Siliceous  iron-ore          .......  1^    " 

5.  Argillaceous  sandstone 75      " 


120  PALEOZOIC   TIME. 

6.  GOAL,  upper  4  feet  shale,  with  fossil  plants,  and  below 

a  thin  clayey  layer 7  feet. 

7.  Sandstone .  80      " 

8.  Iron-Ore      .    .     .         .         .:    -.         .  '      ..        .   '.-.  .  5  1      " 

9.  Argillaceous  shale  .      -.''-•  •.-  •  o^-;*!     t.  :.    t      .  /.    -  t  QQ      u 

10.  LIMESTONE  (oolitic),  containing  Producti,  Crinoids,  etc.  11  " 

11.  Iron- Ore,  with  many  fossil  shells     .         .         .      .  ."  . "".  3  " 

12.  Coarse  sandstone,  containing  trunks  of  trees        .      '  .'  •  '  25  " 

13.  COAL,  lying  on  1  foot  slaty  shale  with  fossil  plants       .  5  " 

14.  Coarse  sandstone     >'-.-'•    '.".  ;    ••.*    •  ..».  i  .:.;  ;  V-i.  k'.-.i  ;  12  " 

The  limestone  strata  are  more  numerous  and  extensive  in 
the  Interior  Continental  region  than  in  the  Appalachian; 
west  of  the  States  of  Missouri  and  Kansas  limestone  is  the 
prevailing  rock. 

Beds  of  argillaceous  iron-ore  or  clay-ironstone  are  very  com- 
mon in  coal-districts,  so  that  the  same  region  affords  ore  and 
the  coal  for  smelting  it.  Some  of  the  largest  iron- works  in 
the  world,  on  both  sides  of  the  Atlantic,  occur  in  coal-dis- 
tricts. The  ore  is  usually  the  carbonate  of  iron,  impure  from 
mixture  with  some  earth  or  clay. 

The  coal-beds  often  rest  on  a  bed  of  grayish  or  bluish  clay, 
called  the  under-day,  which  is  filled  with  the  roots  or  under- 
water stems  of  plants.  When  this  under-clay  is  absent,  the 
rock  below  is  usually  a  sandstone  or  shale.  Above  the  coal- 
bed  the  rock  may  be  sandstone,  shale,  conglomerate,  or  even 
limestone ;  often  the  layer  next  above,  especially  if  shaly,  is 
filled  with  fossil  leaves  and  stems.  In  some  cases,  trunks  of 
old  trees  rise  from  the  coal  and  extend  up  through  overlying 
beds,  as  in  the  annexed  figure,  by  Dawson,  from  the  Nova 
Scotia  Coal-measures.  Occasionally,  as  in  Ohio  and  Penn- 
sylvania, logs  50  to  60  feet  long  lie  scattered  through  the 
sandstone  beds,  looking  as  if  a  forest  had  been  swept  off 
from  the  land  into  the  sea. 

2.  Coal-Beds.  —  The  coal-beds  vary  in  thickness  from  a 
fraction  of  an  inch  to  30  or  40  feet,  but  seldom  exceed  8  feet, 
and  are  generally  much  thinner :  8  to  10  feet  is  the  thickness 
of  the  principal  bed  at  Pittsburg,  Pa. ;  29J  feet,  that  of  the 


CARBONIFEROUS  AGE. 


121 


"  Mammoth  Vein  "  at  Wilkesbarre,  Pa. ;  37  J  feet,  that  of  one 
of  the  two  great  beds  at  Pictou  in  Nova  Scotia.  In  these 
thick  beds,  and  often  also  in  the  thin  ones,  there  are  some  in- 
tervening beds  of  shale,  or  of  very  impure  coal,  so  that  the 
whole  is  not  fit  for  burning. 

Fig.  219. 


Section  of  a  portion  of  the  Coal-measures  at  the  Joggins,  Nova  Scotia,  having  erect  stumps, 
and  also  "rootlets  "  in  the  under-clays. 

The  coal  varies  in  kind,  as  explained  on  page  18,  that  burn- 
ing with  little  flame  being  called  anthracite,  and  that  with 
a  bright  yellow  flame  bituminous  coal.  When  only  12  or  15 
per  cent  of  volatilizable  substances  are  present,  it  is  often 
called  semi-bituminous  coal.  In  Pennsylvania  the  coal  of 
the  Pottsville,  Lehigh,  and  Wilkesbarre  regions  is  anthracite  ; 
that  of  Pittsburg,  bituminous  coal ;  and  that  of  part  of  the  in- 
termediate district,  semi-bituminous,  as  designated  on  the  map, 
page  116. 

The  coal  also  varies  as  to  the  impurities  present.  All  of 
it  contains  more  or  less  of  earthy  material,  and  this  earthy 
material  constitutes  the  ashes  and  slag  of  a  coal-fire.  Ordi- 
nary good  anthracite  contains  7  to  12  pounds  of  impurities 
in  a  hundred  pounds  of  coal,  and  the  best  bituminous  coals  3 
to  7.  In  some  coal-beds  there  is  much  sulphid  of  iron  or 
pyrite  (a  compound  of  sulphur  and  iron),  and  the  coal  is  then 
unfit  for  use.  It  is  seldom  that  the  sulphid  is  altogether 
absent ;  it  is  the  chief  source  of  the  sulphur  gases  that  are 
perceived  in  the  smoke  or  gas  from  a  coal-fire. 


122  PALEOZOIC   TIME. 

Mineral  coal,  although  it  seldom  breaks  into  plates  unless 
quite  impure,  still  consists  of  thin  layers.  Even  the  hardest 
anthracite  is  delicately  banded,  as  seen  on  a  surface  of  frac- 
ture when  it  is  held  up  to  the  light.  This  structure  is  absent 
in  the  variety  called  Cannel  coal,  which  is  a  bituminous  coal, 
very  compact  in  texture,  feeble  in  lustre,  and  smooth  in  frac- 
ture. 

3.  Mineral  Oil.  —  Besides  mineral  coal,  the  rocks  sometimes 
afford,  when  heated,  liquids  consisting  of  carbon  and  hydro- 
gen, called  ordinarily  petroleum  or  mineral  oil,  and  bitumen  ; 
when  purified  for  burning  it  becomes  kerosene.     Oil-wells  are 
largely  worked   at   Titusville,  in   Pennsylvania,  and   about 
Mecca,  in  Trumbull  County,  Ohio,  regions  of  Subcarbonif- 
erous  rocks.     The  wells  are  borings  into  an  inferior  part  of 
the  Subcarboniferous  formation,  or  into  the  upper  part  of  the 
Devonian.     When  a  boring  reaches  the  oil-level,  the  oil  rises 
to  the  surface,  and  sometimes  issues  in  a  jet.    The  oil  is  there- 
fore in  subterranean  cavities,  and  under  pressure.     It  has 
probably  reached  those  cavities  from  some  subjacent  region 
of  oil-yielding  shales  or  limestones.     These  shales,  like  the 
Erie  shale  of  the  Chemung  period,  in  Ohio,  or  the  black  shale 
of  the  Genesee  epoch  of  the  Hamilton  period,  or  the  Utica 
shale  of  the  Lower  Silurian,  are  black  from  the  carbonaceous 
material  penetrating  them ;  and  although  they  do  not  contain 
any  oil  (for  the  solvents  of  it  take  up  none  from  them,  or  but 
traces),  they  contain   compounds   of  carbon   and   hydrogen 
(probably  oxygenated)  which,  when  the  shale  is  heated,  yield 
the  oil  or  liquid  carbo-hydrogen.     Thus  the  shales  are  oil- 
yielding,  though  not  oil-containing.     The  regions  of  wells  are 
mostly  along  lines  of  axes  of  disturbance ;  and  probably  the 
heat  developed  by  the  movement  of  disturbance  caused  the 
production  of  the  oil  and  its  rising  into  any  opened  spaces 
above.     Petroleum  is  a  result  of  the  decomposition  of  vege- 
table or  animal  substances. 

4.  Salt  or  Salines.  —  The   Subcarboniferous   formation   in 
Michigan,  in  the  Saginaw  Valley,  and  in  the  adjoining  region, 


CARBONIFEROUS  AGE.  123 

affords  extensive  salines,  and  many  wells  have  been  opened 
by  boring.  The  beds  affording  the  saline  waters  consist  of 
clayey  beds  or  marlytes,  shale,  and  magnesian  limestone,  and 
abound  also  in  gypsum,  thus  resembling  those  of  the  Salina 
period  in  New  York  (page  94). 

3.  Permian  Period.  —  The  Permian  beds  are  mostly  sand- 
stones and  marlytes,  with  some  impure  magnesian  limestones, 
and  gypsum.  They  occur  in  North  America  west  of  the  Mis- 
sissippi in  Kansas,  where  they  lie  conformably  over  the  Car- 
boniferous. Similar  rocks  occur  in  Great  Britain  in  the 
vicinity  of  several  of  the  coal-regions,  and  also  in  Germany 
and  Eussia.  Thin  seams  of  coal  are  occasionally  interstrati- 
fied  with  the  sandstones,  but  none  of  workable  extent  are 
known. 

4.    Life.    * 

1.    Plants. 

The  plants  of  the  forests,  jungles,  and  floating  islands  of 
the  Carboniferous  age,  thus  far  made  known,  number  about 
900  species.  Among  the  fossils  there  are  none  that  afford 
satisfactory  evidence  of  the  presence  of  either  Angiosperms 
or  Palms  (page  62) ;  for  no  net- veined  leaves,  allied  in  char- 
acter to  those  of  the  Oak,  Maple,  Willow,  Rose,  etc.,  have  been 
found  among  them ;  and  no  palm-leaves  or  palm-wood.  More- 
over, the  plains  were  without  grass,  and  the  swamps  and 
woods  without  moss.  At  the  present  day  Angiosperms, 
along  with  Conifers  or  the  Pine  family,  make  up  the  great 
bulk  of  our  shrubs  and  trees  ;  Palms  abound  in  all  tropical 
countries ;  grass  covers  all  exposed  slopes  where  the  climate 
is  not  too  arid ;  and  mosses  are  the  principal  vegetation  of 
most  open  marshes. 

The  view  in  Fig.  220  gives  some  idea  of  the  Carboniferous 
vegetation  over  the  plains  and  marshes  of  the  era. 

The  Carboniferous  species,  like  their  predecessors  in  the 
Devonian  age,  belonged  to  the  following  groups :  — 


124 


PALEOZOIC   TIME. 
Fig.  220. 


CARBONIFEROUS   AGE. 


125 


I.  Cryptogams,  or  Flowerless  Plants,  Order  of 
Acrogens. 

1,  Fern  Tribe.  —  Ferns  were  very  abundant,  a  large  part  of 
the  fossil  plants  of  a  coal-region  being  their  delicate  fronds 
(usually  called  leaves).  A  portion  of  a  fossil  fern  is  repre- 


Figs.  221-226. 


Fig.  221,  Lepidodendron  aculeatum ;  222,  Sigillaria  oculata;  223,  Stigmaria  ficoides  ;  224, 
Sphenopteris  Gravenhorstii ;  225,  Calamites  eannaeformis  ;  226,  Trigonocarpus  tricuspi- 
datus. 

sented  in  Fig.  224.     Besides  small  species,  like  the  common 
kinds  of  the  present  day,  there  were  Tree-ferns,  species  that 


126  PALEOZOIC   TIME. 

had  a  trunk,  perhaps  20  or  30  feet  high,  and  which  bore  at 
top  a  radiating  tuft  of  the  very  large  leaf-like  fronds,  resem- 
bling the  modern  tree-fern  of  the  tropics.  One  of  the  tree- 
ferns  of  the  Pacific  is  represented  in  Fig.  220,  near  the  middle 
of  the  view,  and  smaller  ferns  in  front  of  it  below.  Tree- 
ferns,  however,  were  not  very  common  in  the  Carboniferous 
forests.  The  scars  in  fossil  or  recent  tree-ferns  are  many 
times  larger  than  those  of  Lepidodendrids,  and  the  fossils  may 
be  thus  distinguished. 

2.  Lycopodium  Tribe.  —  1.  The  Lepidodendrids  appear  to 
have  been  among  the  most  abundant  of  Carboniferous  forest- 
trees,  especially  in  the  earlier  half  of  the  Carboniferous  Age,  or 
to  the  middle  of  the  Coal  Period.  They  probably  covered  both 
the  marshes  and  the  drier  plains  and  hills.  Some  of  the  old 
logs  now  preserved  in  the  strata  are  50  to  60  feet  in  length, 
strikingly  contrasting  with  the  little  Ground- Pines  of  modern 
times ;  and  the  pine-like  leaves  were  occasionally  a  foot  or 
more  long.  The  taller  tree  to  the  left,  on  page  124,  is  a  Lepi- 
dodendron.  Fig.  221  shows  the  surface-markings  of  one  of 
the  species,  natural  size. 

2.  Sigillarids.  —  The  Sigillarice  were  a  very  marked  feature 
of  the  great  jungles  and  damp  forests  of  the  Coal  period. 
They  grew  to  a  height  sometimes  of  30  to  60  feet ;  but  the 
trunks  were  seldom  branched,  and  must  have  had  a  stiff, 
clumsy  aspect,  although  covered   above  with  long,  slender, 
rush-like  leaves.     Fig.  222  represents  a  common  species,  ex- 
hibiting the  usual  arrangement  of  the  scars  in  vertical  lines, 
and  also  indicating,  by  the  difference  in  the  scars  of  the  right 
row  from  those  of  the  others,  their  difference  of  form  on  the 
outer  surface  of  the  tree  and  beneath  the  surface. 

3.  StigmaricB.  —  The  fossil  Stigmarice  are  stout  stems,  gen- 
erally 2  to  3  or  more  inches  thick,  having  over  the  surface 
distinct  rounded  punctures  or  depressions.     Fig.  223  is  a  por- 
tion of  the  extremity  of  a  stem,  showing  the  rounded  depres- 
sions and  also  the  leaf-like  appendages  occasionally  observed. 
The  stems  or  branches  are  a  little  irregular  in  form,  and  spar- 


CARBONIFEROUS   AOE.  127 

ingly  branched.  They  have  been  found  spreading,  like  roots, 
from  the  base  of  the  trunk  of  a  Sigillaria,  and  sometimes  also 
from  that  of  a  Lepidodendron ;  and  they  are  hence  regarded 
either  as  the  roots  or  subaqueous  stems  of  these  trees.  They 
are  an  exceedingly  common  fossil,  especially  in  the  under- 
clays  of  the  Coal-measures  (p.  120). 

3.  Equisetum  Tribe.  —  Fig.  225  represents  a  portion  of  one 
of  the  tree-rushes,  or  Catamites,  of  the  Equisetum  or  Horse- 
tail tribe.  The  specimens  were  very  abundant  in  the  great 
marshes,  through  the  whole  of  the  Carboniferous  Age.  Some 
of  them  were  20  feet  or  more  high  and  10  or  12  inches  in 
diameter. 

Besides  these  Cryptogams  there  were  also  Fungi;  but,  as 
already  stated,  no  remains  of  Mosses  from  the  rocks  of  the 
age  are  known. 

In  the  ideal  view  of  a  Carboniferous  landscape,  Fig.  220, 
page  124,  the  broken  trunk  to  the  right  is  a  Sigillaria.  The 
landscape,  to  be  quite  true  to  nature,  should  have  been  made 
up  largely  of  Sigillarice,  Calamites,  and  Lepidodendra,  with 
few  tree-ferns.  The  Stigmarise  should  have  been  mostly  con- 
cealed beneath  the  water  or  soil,  or  in  the  submerged  mass  of 
the  floating  islands. 

II.  Phenogams,  or  Flowering  Plants,  Order  of 
Gymnosperms. 

1.  Conifers.  —  Trunks  of  trees,  Coniferous  in  character,  and 
related  especially  to  the  Araucanian  pines,  are  not  uncommon. 

2.  Fruits.  —  Besides  the  leaves,  stems,  and  trunks  already 
alluded  to,  there  are  various  nut-like  fruits  found  in  the  Car- 
boniferous strata.     One  is  represented  in  Fig.  226  (page  125), 
the  figure  to  the  left  being  that  of  the  shell,  and  the  other 
that  of  the  nut  which  it  contained.     Some  of  them  are  two 
inches  in  length.     The  most  of  them  were  probably  the  fruit 
of  Conifers. 

It  is  seen  from  the  above  that  — 

1.  The  vegetation  of  the  Carboniferous  age  consisted  very 
largely  of  Cryptogams,  or  flowerless  plants. 


128  PALEOZOIC  TIME. 

2.  The  flowering  plants,  or  Phenogams,  associated  with  the 
flowerless  vegetation,  were   of  the   order   of  Gymnosperms, 
whose  flowers  are  imperfect  and  inconspicuous. 

3.  While,  therefore,  there  was  abundant  and  beautiful  fo- 
liage (for  no  foliage  exceeds  in  beauty  that  of  Ferns),  the 
vegetation  was  nearly  flowerless. 

4.  The  characteristic  Cryptogams  were   not  only  of  the 
highest  group  of  that  division  of  plants,  but  in  general  they 
exceeded  in  size  and  perfection  the  species  of  the  present  day, 
many  being  forest-trees. 

2.   Animals. 

1.  Radiates.  —  Among  Radiates,  species  of  Crinoids  were 
especially  numerous  in  the  Subcarboniferous  period.     Figs, 
227,  228,  229  represent  some  of  the  species.     The  radiating 
arms  are  perfect  in  Fig.  227,  but  wanting  in  228.     Fig.  229 
is  a  species  of  the  genus  Pentremites  (named  from  the  Greek 
7rei/T€,  five,  alluding  to  the  five-sided  form  of  the  fossil).     The 
Pentremites  had  a  stem  made  of  calcareous  disks,  like  other 
Crinoids,  but  no  long  radiating  arms  at  top. 

Fig.  230  presents  an  upper  view  of  a  very  common  Coral 
of  the  same  period :  it  has  a  columnar  appearance  in  a  side 
view.  * 

2.  Mollusks.  —  The  tribe  of  Bryozoans  contained  the  singu- 
lar screw-shaped  (or  auger-shaped)  Coral  shown  in  Fig.  231, 
and  named  Archimedes  (referring  to  Archimedes's  screw).     It 
is  made  up  of  minute  cells  that  open  over  the  lower  surface  ; 
each  of  the  cells,  when  alive,  contained  a  minute  Bryozoum 
(page  57).     These  fossils  are  common  in  some  of  the  Subcar- 
boniferous limestone  strata. 

Brachiopods  were  the  most  abundant  of  Mollusks  through 
the  Carboniferous  age,  and  especially  species  of  the  genera 
Spirifer  and  Productus.  Figs.  232  to  235  are  of  species  from 
the  American  Coal-measures:  Fig.  234,  a  Spirifer ;  Fig.  233, 
a  Productus ;  Fig.  232,  a  Chonetes ;  Fig.  235,  an  Athyris,  oc- 
curring also  in  Europe.  Fig.  236  represents  one  of  the  Gas- 


CARBONIFEROUS  AGE. 


129 


teropods  of  the  Coal-measures.     Fig.  237  is  a  Pupa,  the  earli- 
est yet  found  of  land-snails :  it  is  from  the  Coal-measures  of 


Pigs.  227-237. 


231 


RADIATES :  Fig.  227,  Zeaerinus  elegans ;  228,  Aetinocrinus  proboscidialis ;  229,  Pentre- 
mites  pyriformis ;  230,  Lithostrotion  Canadense.  —  MOLLUSKS  :  Fig.  231,  Archimedes 
reversa ;  232,  Chonetes  mesoloba  ;  233,  Productus  Nebrascensis  ;  234,  Spirifer  cameratus  ; 
235,  Athyris  subtilita ;  236,  Pleurotomaria  tabulata  ;  237,  Pupa  vetusta. 

Nova  Scotia ;  others  have  been  found  in  Illinois.  The  order 
of  Cephalopods  contained  but  few  and  small  species  of  the 
old  tribe  of  Orthocerata,  but  many  of  the  Ammonite-like  GrO- 

niatites. 

6*  I 


130 


PALEOZOIC  TIME. 


3.  Articulates.  —  Among  Articulates,  Crustaceans  appeared 
under  a  new  form,  much  like  that  of  modern  shrimps,  and 
Trilobites  were  of  rare  occurrence. 

Figs.  238-240. 


sa. 


SPIDERS  :  Fig.  238,  Arthrolycosa  antiquus  ;   239,  Eoscorpius  carbonarius.  —  INSECT : 
Fig.  240,  Miainia  Bronsoni. 

Besides  Insects  (Fig.  240),  there  were  also  Myriapods,  true 
Spiders  (Fig.  238),  and  Scorpions  (Fig.  239) ;  the  figures  are 
of  Illinois  species.  The  Insects  include  May-flies  (Neurop- 
ters),  Locusts  and  Cockroaches  (or  Orthopterous  insects),  and 
Beetles  (or  Coleopters). 

4.  Vertebrates.  —  Fishes  were  numerous,  both  of  the  orders 
of  Ganoids  and  Selachians.  All  the  Ganoids  were  of  the  an- 


CARBONIFEROUS  AGE. 


131 


cient  type,  having  the  tail  vertebrated  (or  heterocercal),  as 
in  Fig.  241,  representing  a  Permian  species  of  Palceoniscus. 
Many  of  the  Selachians,  or  Sharks,  were  of  great  size,  as 
shown  by  the  fin-spines.  Fig.  242  represents  a  small  portion 
of  one  of  these  spines,  natural  size,  from  the  Subcarboniferous 
beds  of  Europe.  One  of  the  largest  specimens  of  the  same 
species  thus  far  found  had  a  length  of  14J  inches,  and  when 
entire  it  must  have  been  full  18  inches  long. 

Figs.  241,  242. 


Fig.  241,  Palseoniscus  Freieslebeni  (x£);  242,  Part  of  a  spine  of  Ctenacanthus  major. 

The  first  traces  of  Eeptiles  yet  known  occur  in  the  Subcar- 
boniferous beds  of  Pottsville,  Pennsylvania. 

Fig.  243  is  a  reduced  sketch  of  a  slab  containing  tracks  of 
the  species,  and  also  an  impression  left  by  the  tail  of  the  ani- 
mal. The  tracks  of  the  fore-feet,  as  described  by  Dr.  Lea,  are 
5-fingered  and  4  inches  broad,  and  'those  of  the  hind  feet 
4-fingered  and  nearly  of  the  same  size ;  while  the  stride  indi- 
cated was  13  inches.  Fig.  244  represents  a  skeleton  of  an 
Amphibian  from  the  Ohio  Coal-measures,  found  by  Newberry  ; 
and  Fig.  245  a  vertebra  of  a  swimming  Saurian  probably  re- 


132 


PALEOZOIC  TIME. 


lated  to  the  Enaliosaurs,  or  Sea-Saurians,  of  the  Mesozoic  (see 
page  174),  discovered  by  Marsh  in  the  Coal-measures  of  Nova 


Pigs.  243-245. 


Fig.  243,  Tracks  of  Sauropus  priinsevus  (x  |);  244,  Raniceps  Lyellii ;  245,  a.  Vertebra  of 
Eosaurus  Acadianus. 

Scotia.  This  vertebra  is  concave  on  both  surfaces,  as  shown 
in  the  section  in  Fig.  245  a,  and  in  this  respect  resembles 
those  of  fishes.  The  Enaliosaurs  had  paddles  like  Whales.  . 


CARBONIFEROUS  AGE.  133 

These  Enaliosaurs,  or  swimming  Eeptiles,  are  the  highest 
species  of  animal  yet  discovered  in  rocks  of  the  Carboniferous 
period.  In  the  Permian  period  there  were  still  higher  Eep- 
tiles, somewhat  Crocodile-like,  called  Thecodonts  (because  the 
teeth  are  set  in  sockets,  from  the  Greek  Qr\icT),  case,  and  oSovs, 
tooth).  But  these  also  had  the  fish-like  characteristic  of 
doubly-concave  vertebrae. 

5.  General  Observations. 

1.  Formation  of  Coal,  and  origin  of  the  Coal-measures.  —  7. 

Origin  of  the  Coal.  —  The  vegetable  origin  of  coal  is  proved 
by  the  following  facts  :  — 

1.  Trunks  of  trees,  retaining  still  the  original  form  and 
part  of  the  structure  of  the  wood,  have  been  found  changed 
to  mineral  coal,  both  in  the  Carboniferous  strata  and  in  more 
modern  formations,  showing  that  the  change  may  and  does 
take  place. 

2.  Beds  of  peat,  a  result  of  vegetable  growth  and  accumu- 
lation, exist  in  modern  marshes ;  and  in  some  cases  they  are 
altered  below  to  an  imperfect  coal.     (See  page  265,  on  the 
formation  of  peat.) 

3.  Eemains  of  plants,  their  leaves,  branches,  and  stems  or 
trunks,  abound  in  the  Coal-measures ;  trunks  sometimes  ex- 
tend upward  from  a  coal-bed  into  and  through  some  of  the 
overlying  beds  of  rock ;  roots  or  stems  abound  in  the  under- 
clays. 

4.  The   hardest   anthracite  contains  throughout   its   mass 
vegetable  tissues.     Professor   Bailey  examined  with  a  high 
magnifying  power  several  pieces  of  anthracite  burnt  at  one 
end,  like  Fig.  246,  taking  fragments  from  the  junction  of  the 
white  and  black   portion,  and  detected  readily  the  tissues. 
Fig.  247  represents  the  ducts,  as  they  appeared  in  one  case 
under  his  microscope ;  and  Fig.  247  a  part  of  the  same,  more 
magnified.     Fig.  248  shows  the  appearance  of  the  spores  of 
Lycopods  (Lepidodendrids)  much  magnified ;  they  are  com- 
mon in  coal. 


134 


PALEOZOIC   TIME. 


2.  Decomposition  of  Vegetable  Material.  —  The  Mineral  Coal  of 
the  Coal-measures  consists  (impurities  excluded)  of  77  to  97 
per  cent  of  carbon  along  with  2  to  6  of  hydrogen  and  2  to  15 
of  oxygen ;  and  woody  material,  whether  of  Conifers,  Ferns, 
Lycopods,  or  Equiseta,  consists  of  about  50  per  cent  of  car- 
bon, 6  of  hydrogen,  and  44  of  oxygen. 


To  change  the  wood 


Figs.  246  -247  a. 


247  n 


Fig.  248. 


Vegetable  tissues  in  Anthracite. 

or  vegetable  material  to  coal,  it  is  necessary  to  get  rid  of  part 
of  the  oxygen  and  hydrogen.     Vegetable  matter  decomposing 

in  the  open  air  —  like  wood 
burnt  in  an  open  fire  —  passes, 
carbon  and  all,  into  gaseous 
combinations,  and  little  or  no 
carbon  is  left  behind.  But 
when  it  is  decomposed  slowly 
under  water,  or  by  a  half- 
smothered  fire,  only  part  of 
the  carbon  is  lost  in  gaseous 
combinations,  the  rest  re- 
maining in  combination  with 
a  portion  of  the  hydrogen 

Spores  and  part  of  a  Sporangium  in  bitumi-  n    „__„    _  j  _       ji    J 

nous  coal  of  Ohio  (x  70).  oxygen  as  coal,  — 

mineral   coal    in    the   former 
case,  and  charcoal  in  the  latter. 

The  actual  loss,  by  weight,  in  the  transformation  into  bitu- 


CARBONIFEROUS  AGE.  135 

minous  coal,  is  at  least  three  fifths  of  the  wood,  and  in  that  into 
anthracite,  three  fourths.  Adding  to  this  loss  that  from  com- 
pression, by  which  the  material  is  brought  to  the  density  of 
mineral  coal,  the  whole  reduction  in  bulk  is  not  less  than  to 
one  fifth  for  the  former,  and  to  one  eighth  for  the  latter.  In 
other  words,  it  would  take  5  feet  of  vegetable  matters  to  make 
1  of  bituminous  coal,  and  8  feet  to  make  1  of  anthracite. 

8.  Impurities  in  Coal.  —  The  coal  thus  formed  would  have  de- 
rived some  silica  and  other  earthy  ingredients  from  the  wood 
itself,  and  alumina  from  the  Lepidodendrids,  this  earth  exist- 
ing in  the  ash  of  modern  Lycopods.  By  this  means  the  best 
coal  received  the  earthy  impurities  which  give  rise  to  the 
ashes  and  slag  formed  in  a  hot  fire;  while  the  poorer  coals 
contain  clay  or  earthy  material  carried  over  the  marshes  by 
the  waters  or  winds. 

4.  Accumulation  and  Formation  of  Coal-beds.  —  The  origin  of 
coal-beds  was,  then,  as  follows :  The  plants  of  the  great 
marshes  and  shallow  lakes  of  the  Coal  era,  the  latter  with 
their  floating  islands  of  vegetation,  continued  growing  for  a 
long  period,  dropping  annually  their  leaves,  and  from  time  to 
time  decaying  stems  or  branches,  until  a  thick  accumulation 
of  vegetable  remains  was  formed,  —  probably  5  feet  in  thick- 
ness for  a  one-foot  bed  of  bituminous  coal.  The  bed  of  ma- 
terial thus  prepared  over  the  vast  wet  areas  of  the  continent 
early  commenced  to  undergo  at  bottom  that  slow  decomposi- 
tion the  final  result  of  which  is  mineral  coal.  But,  as  the 
coal-beds  alternate  with  sandstones,  shales,  conglomerates,  and 
limestones,  the  long  period  of  verdure  was  followed  by 
another  of  overflowing  waters,  —  and  generally,  in  the  case 
of  the  region  of  the  Interior  basin  of  North  America,  oceanic 
waters,  as  the  fossils  prove,  —  which  carried  sands,  pebbles, 
or  earth,  over  the  old  marsh,  till  scores  or  hundreds  of  feet  in 
depth  of  such  deposits  had  been  made.  Thus  the  bed  of 
vegetable  material  was  buried ;  and  under  this  condition  the 
process  of  decomposition  and  change  to  mineral  coal  went 
forward  to  its  completion ;  it  had  the  smothering  influence  of 


136  PALEOZOIC  TIME. 

the  burial,  as  well  as  the  presence  of  water,  to  favor  the  pro- 
cess. 

5.  Climate  of  the  Age.  —  The  wide  distribution  of  the  coal 
regions  over  the  globe,  from  the  tropics  to  remote  Arctic 
lands,  and  the  general  similarity  of  the  vegetable  remains  in 
the  coal-beds  of  these  distant  zones,  prove  that  there  was  a 
general  uniformity  of  climate  over  the  globe  in  the  Carbon- 
iferous age,  or  at  least  that  the  climate  was  nowhere  colder 
than  warm-temperate.     Besides,  corals  and  shells  existed  dur- 
ing the  Subcarboniferous  period  in  Europe,  the  United  States, 
and  the  Arctic  within  20°  of  the  north  pole,  and  so  profusely 
as  to  form  thick  limestones  out  of  their  accumulations ;  and 
some  Arctic  species  are  identical  with  those  of  Europe  and 
America.     The  ocean's  waters,  even  in  the  far  north,  were, 
therefore,  warm  compared  with  those  of  the  modern  temper- 
ate zone,  and  probably  quite  as  warm  as  the  coral-reef  seas 
of  the  present  age,  which  lie  mostly  between  the  parallels  of 
28°  either  side  of  the  equator. 

6.  Atmosphere.  —  The  atmosphere  was  especially  adapted  for 
the  age  in  other  respects.     It  contained  a  larger  amount  than 
now  of  carbonic-acid  gas,  —  the  gas  which  promotes  (if  not  in 
excess)  the  growth  of  vegetation.     Plants  derive  their  carbon 
mainly  from  the  carbonic  acid  of  the  atmosphere ;  and  hence 
the  mineral  coal  of  the  world  is  approximately  a  measure  of 
the  amount  of  carbonic  acid  the  atmosphere  in  the  Carboni^ 
erous  era  lost.     The  growth  of  the  flora  of  that  age  was  a 
means  of  purifying  the  atmosphere  so  as  to  fit  it  for  the  higher 
terrestrial  life  that  was  afterward  to  possess  the  world. 

Again,  the  atmosphere  was  more  moist  than  now.  This 
follows  from  the  greater  heat  of  the  climate  and  the  greater 
extent  as  well  as  higher  temperature  of  the  oceans.  The  con- 
tinents, although  large  during  the  intervals  of  verdure  com- 
pared with  the  areas  above  the  ocean  in  the  Devonian  or  Si- 
lurian, were  still  small  and  the  land  low.  It  must,  therefore, 
have  been  an  era  of  prevailing  clouds  and  mists.  A  moist 
climate  would  not,  however,  have  been  universal,  since  even 


CARBONIFEROUS  AGE.  137 

the  ocean  has  now  its  great  areas  of  drought  depending  on  the 
courses  of  the  winds.  America  is  now  the  moist  forest- conti- 
nent of  the  globe ;  and  the  great  extent  of  the  coal-fields  of 
its  northern  half  proves  that  it  bore  the  same  character  in  the 
Carboniferous  age. 

2.  Geography.  —  7.  Appalachian  and  Rocky  Mountains  not  made. 
—  On  page  114  it  is  stated  that  the  continents  in  this  age 
were  low,  with  few  mountains.  The  non-existence  of  the 
Appalachians  of  Pennsylvania  and  Virginia  is  proved  by  the 
fact  that  the  rocks  of  these  mountains  are  to  a  considerable 
extent  Carboniferous  rocks;  —  partly  marine  rocks,  indicat- 
ing that  the  sea  then  spread  over  the  region ;  partly  coal-beds, 
each  bed  evidence  that  a  great  fresh- water  marsh,  flat  as  all 
marshes  are,  for  a  long  while  occupied  the  region  of  the  pres- 
ent mountains. 

There  is  the  same  evidence  that  the  mass  of  the  Rocky 
Mountains  had  not  been  lifted;  for  marine  Carboniferous 
rocks  constitute  a  large  part  of  these  mountains,  many  beds 
containing  remains  of  the  life  of  the  Carboniferous  seas  that 
covered  that  part  of  North  America.  Only  islands,  or  archi- 
pelagoes of  islands,  made  by  some  Arcli£ean  and  perhaps 
also  Paleozoic  ridges,  existed  in  the  midst  of  the  widespread 
western  waters. 

2.  Condition  in  the  Subcarboniferous  Period.  —  Through  the  first 
period  of  this  age  —  the  Subcarboniferous  —  the  continent 
was  almost  as  extensively  beneath  the  sea  as  in  the  Devonian 
age.  This,  again,  is  shown  by  the  nature  and  extent  of  the 
Subcarboniferous  rocks,  —  the  great  crinoidal  limestones. 
The  shallow  continental  seas  were  profusely  planted  with 
Crinoids  amid  clumps  of  Corals.  Brachiopods  were  here  and 
there  in  great  abundance,  many  lying  together  in  beds  as  oys- 
ters in  an  oyster-bed;  other  Mollusks,  both  Lamellibranchs 
and  Gasteropods,  were  also  numerous ;  Trilobites  were  few ; 
Goniatites  and  Nautili,  along  with  Ganoid  Fishes  and  Sharks, 
were  the  voracious  life  of  the  seas,  and  Amphibian  reptiles 
haunted  the  marshes. 


138  PALEOZOIC   TIME. 

8.  Transition  to  the  Carboniferous  Period.  —  Finally,  the  Sub- 
carboriiferous  period  closed,  and  the  Carboniferous  opened. 
But  in  the  transition  from  the  period  of  submergence  to  that 
of  emergence,  required  to  bring  into  existence  the  great 
marshes,  a  widespread  bed  of  pebbles,  gravel,  and  sand  was 
accumulated  by  the  waves  dashing  rudely  over  the  surface  of 
the  rising  continent;  and  these  pebble-beds  make  the  Mill- 
stone grit  that  marks  the  commencement  of  the  Carboniferous 
period  in  a  large  part  of  Eastern  North  America,  especially 
along  the  Appalachian  region,  and  also  in  Europe. 

4.  Coal-plant  Areas  in  the  Carboniferous  Period.  —  Then  began 
the  epoch  of  the  Coal-measures. 

The  positions  of  the  great  coal  areas  of  North  America 
(see  map,  page  69)  are  the  positions,  beyond  question,  of  the 
great  marshes  and  shallow  fresh-water  lakes  of  the  period. 
But  it  is  probable  that  the  number  of  these  marshes  was  less 
than  that  of  the  coal  areas.  The  Appalachian,  Illinois,  Mis- 
souri, Arkansas,  and  Texas  fields  may  have  made  one  vast 
Interior  continental  marsh-region,  and  those  of  Rhode  Island, 
Nova  Scotia,  and  New  Brunswick  an  Eastern  border  marsh- 
region  connected  over  Massachusetts  Bay  and  the  Bay  of 
Fundy.  There  is  reason,  however,  for  believing  that  a  low 
area  of  dry  land  extending  from  the  region  of  Cincinnati  into 
Tennessee  (page  91)  divided  at  least  the  northern  portion 
of  the  Interior  marsh. 

The  Michigan  marsh-region  appears  also  to  have  had  its 
dry  margins,  instead  of  coalescing  with  the  Illinois  or  Ohio 
areas. 

It  is  not  to  be  inferred  that  the  marshes  alone  were  cov- 
ered with  verdure.  The  vegetation  probably  spread  over  all 
the  dry  land,  though  making  thick  deposits  of  vegetable  re- 
mains only  where  there  were  marshes  under  dense  jungles 
and  shallow  lakes  with  their  floating  islands. 

5.  Alternations  of  Condition:  Changes  of  Level.  —  It  has  been 
remarked  that  the  many  alternations  of  the  coal-beds  with 
sandstones,  shales,  conglomerates,  and  limestones  (page  119), 


CARBONIFEROUS  AGE.  139 

are  evidence  of  as  many  alternations  of  level,  or  at  least  of 
conditions,  during  the  era.  After  the  great  marshes  of  the 
Continental  Interior  had  been  long  under  verdure,  the  salt 
waters  began  again  to  encroach  upon  them  in  consequence  of 
a  sinking  of  the  land,  and  finally  swept  over  the  whole  surface, 
destroying  the  terrestrial  and  fresh- water  life  of  the  area, — that 
is,  the  terrestrial  and  fresh- water  Plants,  Mollusks,  Insects,  and 
Eeptiles,  —  but  distributing  at  the  same  time  the  new  life  of 
the  salt  waters.  Then,  after  another  long  period,  one  perhaps 
of  many  oscillations  in  the  water-level,  in  which  sedimentary 
beds  in  many  alternations  were  formed,  the  continent  again 
rose  to  aerial  life,  and  the  marshes  and  shallow  lakes  were 
luxuriant  anew  with  the  Carboniferous  vegetation.  Thus  the 

O 

sea  prevailed  at  intervals  —  intervals  of  long  duration — - 
through  the  era  even  of  the  Coal-measures ;  for  the  associated 
sedimentary  beds,  as  has  been  stated,  are  at  least  fifty  times 
as  thick  as  the  coal-beds.  In  the  Nova  Scotia  Coal  area,  the 
waters  which  came  in  over  the  coal-beds  were  the  brackish 
or  fresh  waters  of  a  great  estuary,  —  that  at  the  mouth  of  the 
St.  Lawrence  River  of  the  Carboniferous  period. 

These  oscillations  continued  until  3,000  to  4,000  feet  of 
strata  were  formed  in  Pennsylvania,  and  over  .14,000  in  Nova 
Scotia. 

The  Carboniferous  period  was,  therefore,  ever  varying  in 
its  geography.  A  map  of  its  condition  when  the  great  coal- 
beds  were  accumulating  would  have  its  eastern  coast-line  not 
far  inside  of  the  present,  and  in  the  region  of  Nova  Scotia 
and  New  England  even  outside  of  the  present ;  for  there  must 
have  been  a  sea-barrier  in  order  that  the  deposits  in  the  for- 
mer region  should  have  been  of  brackish  or  fresh-water  origin. 
The  southern  coast-line  would  pass  through  central  Carolina, 
Georgia,  Alabama,  and  Northern  Mississippi,  then  west  of 
the  Mississippi,  around  Arkansas  and  the  bordering  counties 
of  Texas ;  thence  it  would  stretch  northward,  bounding  a 
sea  covering  a  large  part  of  the  Rocky-Mountain  region,  for 
the  Coal  period  was,  in  that  part  of  the  continent,  mainly  a 


140  PALEOZOIC  TIME. 

time  of  limestone-making.  On  the  contrary,  in  a  map  repre- 
senting it  during  the  succeeding  times  of  submergence,  the 
coast-line  would  run  through  Southeastern  New  England,  then 
near  the  southern  boundary  of  New  York  State,  then  north- 
westward around  Michigan,  then  southward  again  to  Northern 
Illinois,  and  then  westward  and  northwestward  to  the  Upper 
Missouri  region,  or  the  Eocky  Mountain  sea.  Through  these 
conditions,  as  the  extremes,  the  continent  passed  several 
times  in  the  course  of  the  Carboniferous  period. 

6.  Condition  in  the  Permian  Period.  —  Finally,  in  the  Permian 
period,  the  Appalachian  region,  and  the  Interior  region  east 
of  a  north-and-south  line  running  through  Missouri,  appear 
to  have  been  mainly  above  the  ocean ;  for  the  Permian  beds 
are  mostly  confined  to  the  meridians  of  Kansas  and  the 
remoter  West. 


GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC. 

1.  Rocks,  —  7.  Maximum  thickness.  —  The  maximum  thick- 
ness of  the  rocks  of  the  Silurian  age  in  North  America  is  *at 
least  25,000  feet ;  of  the  Devonian,  about  14,400  feet ;  and  of 
the  Carboniferous  age,  about  16,000  feet. 

2.  Diversities  of  the  different  Continental  regions  as  to  kinds  of 
rocks.  —  The  Paleozoic  rocks  of  the  Appalachian  region  are 
mainly  sandstones,  shales,  and  conglomerates ;  only  about  one 
fourth  in  thickness  of  the  whole  consists  of  limestone.     The 
rocks  of  the  Interior  Continental  are  mostly  limestone,  full 
two  thirds  being  of  this  nature. 

The  difference  of  these  two  regions,  in  this  particular,  will 
be  appreciated  on  comparing  the  following  general  section  of 
the  strata  of  the  Interior  with  the  section,  on  page  67,  of  the 
rocks  of  New  York,  —  New  York  State  lying  on  the  inner 
border  of  the  Appalachian  region.  The  Lower  Silurian  beds 
in  the  Mississippi  basin,  as  the  section  shows,  consist  mainly 
of  limestones ;  so  also  the  Upper  Silurian,  Devonian,  and  Sub- 
carboniferous  formations ;  and  the  Carboniferous  of  the  region 


GENERAL   OBSERVATIONS. 


141 


contains  more  limestone  than  that  of  the  East.  In  the  Devo- 
nian of  the  Interior  the  Hamilton  is  represented  by  a  lime- 
stone in  parts  of  Michigan,  Ohio,  Canada  West,  and  Illinois, 
to  Iowa,  and  besides  this  there  is  only  a  black  shale,  one  to 
three  or  four  hundred  feet  thick. 

In  the  Eastern-border  region,  about  the  Gulf  of  St.  Law- 
rence, there  is  a  great  predominance  of  limestones  in  the 


Pig.  249. 


Permian 

Carboniferous 


Subcarboniferous 


Chemung  ... 
(  Hamilton 

(  Corniferous 


Niagara j 

Cincinnati j 

Trenton j 

Canadian j 

Potsdam J 


Permian. 
Coal  Measures. 

Coal  Conglomerate. 
Subcarboniferous  limestone. 

Subcarboniferous  sandstone. 
Black  shale. 
Cliff  limestone. 

Blue  limestone  and  shale. 

Trenton  limestone  ;  Galena 
limestone ;  Black  River 
limestone. 

Lower  Magnesian  limestone 
(=  Calciferous). 

Potsdam  sandstone. 


Section  of  the  Paleozoic  rocks  in  the  Mississippi  basin. 

formations.  They  prove  the  existence  in  that  region  of  an 
Atlantic-border  basin  similar  in  some  respects  to  the  basin  of 
the  Interior,  —  the  two  being  separated  by  the  Green  Moun- 
tains, that  is,  the  northern  part  of  the  Appalachian  region. 

3.  Diversities  of  the  Appalachian  and  Interior-Continental  regions 
as  to  the  thickness  of  the  rocks.  —  In  the  Appalachian  region 
the  maximum  thickness  of  the  Paleozoic  rocks  is  about  50,000 
feet.  But  this  thickness  is  not  observed  at  any  one  locality, 
it  being  obtained  by  adding  together  the  greatest  thicknesses 
of  the  several  formations  wherever  observed.  The  greatest 
actual  thickness  at  anyone  place  in  Pennsylvania  is  about 
40,000  feet,  or  over  seven  miles. 


142  PALEOZOIC   TIME. 

In  the  central  portions  of  the  Interior-Continental  region 
the  thickness  varies  from  3,500  feet  (and  still  less  on  the 
northern  border)  to  6,000  feet ;  and  it  is,  therefore,  from  one 
sixth  to  one  tenth  that  in  the  Appalachian  region. 

4.  Origin  of  the  deposits.  —  The  material  of  the  fragmental 
rocks,  or  those  of  sand,  clay,  mud,  pebbles  (the  sandstones, 
shales,  earthy  sandstones  and  conglomerates),  was  "made  (1) 
by  the  wear  of  pre-existing  rocks  under  the  action  of  water ; 

(2)  by  disintegration  produced  by  partial  decomposition ;  and 

(3)  by  disaggregation  from  expansion  and  contraction  due  to 
daily  and  annual  changes  of  temperature.     The  water  was 
mainly  that  of  the  ocean,  and  the  power  was  that  of  its  waves 
and  currents.     But  the  water  from  the  rains  aided  in  the 
wear,  although  there  were  no  large  rivers ;  and,  through  the 
carbonic  acid  it  took  up  from  the  atmosphere,  it  was  a  great 
agent  in  the  disintegration  of  exposed  rocks,  —  feldspar,  the 
most  common  ingredient  in  crystalline  rocks  and  also  nearly 
all  iron-bearing  minerals,  yielding  more  or  less  easily  under 
the  action. 

The  material  of  the  coarser  rocks  may  have  accumulated 
where  the  waves  were  dashing  against  a  beach  or  an  exposed 
sand-reef,  or  else  where  currents  were  in  rapid  movement 
over  the  bottom;  for  accumulations  of  pebbles  and  coarse 
sand  are  now  made  under  these  circumstances.  The  material 
of  the  earthy  sandstones  may  have  been  the  mud  or  earthy 
sands  forming  the  bottom  of  shallow  seas.  The  fine  clayey 
or  earthy  deposits  must  have  been  made  in  either  sheltered 
bays  or  interior  seas,  in  which  the  waves  were  light,  and 
therefore  fitted  to  produce  by  their  gentle  attrition  the  finest 
of  mud ;  or  else  in  the  deeper  off-shore  waters,  where  the  finer 
detritus  of  the  shores  is  liable  to  be  borne  by  the  currents. 

Accumulations  of  any  degree  of  thickness  may  be  made  in 
shallow  waters,  provided  the  region  is  undergoing  very  slow 
subsidence ;  for  in  this  way  the  depth  of  the  waters  may  be 
kept  sufficient  to  allow  of  constantly  increasing  depositions. 
Thus,  by  a  slow  subsidence  of  1,000  feet,  deposits  1,000  feet 


GENERAL  OBSERVATIONS.  143 

thick  may  be  produced,  and  the  depth  of  water  at  no  time 
exceed  20  feet.  The  occurrence  of  ripple-inarks,  mud-cracks, 
or  rain-drop  impressions  in  many  beds  of  most  of  the  forma- 
tions proves  that  the  layers  so  marked  were  successively  near 
the  surface,  and  therefore  that  there  must  have  been  a  grad- 
ual sinking  of  the  bottom  as  the  beds  were  formed. 

The  limestones  of  the  Paleozoic  were  probably  made,  in 
every  case,  out  of  organic  remains,  either  Shells,  Corals,  Cri- 
noids,  etc.,  or  the  minute  Khizopods,  which  are  known  to 
have  formed,  to  a  large  extent,  the  chalk-beds  of  Europe. 
Shells,  Corals,  and  Crinoids  must  be  ground  up  by  the  waves  to 
form  fine-grained  rocks ;  while  the  shells  of  Ehizopods  are  so 
minute  as  to  be  already  fine  grains,  and  may  become  compact 
rocks  by  simple  consolidation. 

The  hornstone  in  the  limestones,  as  remarked  on  page  108, 
may  be  wholly  of  organic  origin. 

2.  Time-Ratios.  —  Judging  from  the  maximum  thickness  of 
the  rocks  of  the  several  Paleozoic  ages  in  North  America,  and 
allowing  that  five  feet  of  fragmental  rocks  may  accumulate 
in  the  time  required  for  one  foot  of  limestone,  the  relative 
lengths  of  the  Silurian,  Devonian,  and  Carboniferous  ages 
were  not  far  from  4 :  1 :  1,  and  the  Lower  Silurian  era  was 
four  times  as  long  as  the  Upper. 

Time  moved  on  slowly  in  the  earth's  first  beginnings.  The 
condition  of  the  earth  in  an  age  of  Invertebrates,  when  all  life 
was  the  life  of  the  waters,  and  nothing  existed  above  the 
ocean's  level  except  it  may  be  the  humble  lichen  or  fungus, 
was  very  inferior  to  that  of  the  Carboniferous,  when  the  con- 
tinents had  their  forests,  the  waters  their  fishes,  and  the 
marshes  their  reptiles.  Yet  the  length  of  time  through  which 
the  earth  was  groping  under  the  first-mentioned  condition 
was  vastly  longer  than  under  the  last.  Such  is  time  in  the 
view  of  the  infinite  Creator. 

3.  Geography.  —  7.  Close  of  Archcean  time.  —  The  map  on  page 
73  shows  approximately  the  outline  of  the  dry  land  of  North 
America  at  the  close  of  the  Archaean.     The  only  mountains 


144  PALEOZOIC  TIME. 

were  Archsean  mountains,  the  principal  of  which  were  the 
Laurentian  of  Canada,  the  Adirondacks  of  Northern  New  York, 
the  Highlands  of  New  Jersey  and  Dutchess  County  of  New 
York,  the  Blue  Kidge  farther  to  the  southwest,  and  the  Wind- 
River  and  other  eastern  ridges  of  the  Eocky  Mountain  region. 
We  qannot  judge  of  the  height  of  these  mountains  then  from 
what  we  now  see,  after  all  the  ages  of  Geology  have  passed 
over  them,  for  the  elements  and  running  water  have  never 
ceased  action  since  the  time  of  their  uplift,  and  the  amount 
of  loss  by  degradation  must  have  been  very  great. 

2.  General  Progress  through  Paleozoic  time.  —  The  increase  of 
dry  land  during  the  Paleozoic  has  been  shown  (pages  99, 113) 
to  have  taken  place  mainly  along  the  borders  of  the  Archsean, 
so  that  the  original  area  was  thus  gradually  extending.     This 
increase  is  well  marked  from  north  to  south  across  New  York. 
At  the  close  of  the  Lower  Silurian  the  shore-line  was  not  far 
from  the  present  position  of  the  Mohawk,  indicating  but  a 
slight  extension  of  the  dry  land  in  the  course  of  this  very 
long  era;  when   the   Upper   Silurian   ended,  the   shore-line 
probably  extended  along  a  score  of  miles  or  so  south  of  the 
Mohawk.     When  the  Devonian  ended  and  the  Carboniferous 
age  was  about  opening,  the  coast-line  was  just  north  of  the 
Pennsylvania  boundary. 

The  progress  southward  was  at  an  equal  rate  in  Wisconsin, 
where  there  is  an  isolated  Archaean  region  like  that  of  North- 
ern New  York.  In  the  intermediate  district  of  Michigan  the 
coast  made  a  deep  northern  bend  through  the  Silurian  and 
Devonian.  In  the  Carboniferous  the  same  great  Michigan 
bay  existed  during  the  intervals  of  submergence ;  but  it  was 
changed  to  a  Michigan  marsh  or  fresh-water  lake,  filled  with 
Coal-measure  vegetation,  during  the  intervening  portions  of 
the  Carboniferous  period ;  and,  at  the  same  times,  as  explained 
on  page  139,  the  continent  east  of  the  western  meridian  of 
Missouri  had  nearly  its  present  extent,  though  not  its  moun- 
tains or  its  rivers. 

3.  Regions  of  rock-making,  and  their  differences.  —  The  sub- 


GENERAL  OBSERVATIONS.  145' 

merged  part  of  the  continent  was  the  scene  of  nearly  all  the 
rock-making ;  and  this  work  probably  went  on  over  its  whole 
wide  extent. 

The  rocks,  as  partially  explained  on  page  142,  varied  in 
kind  with  the  depth,  and  with  the  exposure  to  the  open  sea. 

This  Interior  Continental  region,  which  was  for  the  most  of 
the  time  a  great  interior  oceanic  sea,  afforded  the  conditions 
fitted  for  the  growth  of  Corals  and  Crinoids  and  other  clear- 
water  species,  and  hence  for  the  making  of  limestone  reefs 
out  of  their  remains ;  for  limestones  are  the  principal  rocks 
of  the  Interior.  Yet  there  were  oscillations  in  the  level ;  for 
there  are  abrupt  transitions  in  the  limestones,  and  some  sand- 
stones and  shales  alternate  with  them.  But  these  oscillations 
were  not  great,  the  whole  thickness  of  the  rocks,  as  stated  011 
page  142,  being  small 

The  Appalachian  region,  on  the  contrary,  presented  the 
conditions  required  for  fragmental  deposits.  It  was  appar- 
ently a  region  of  immense  sand-reefs  and  mud-flats,  with 
bays,  estuaries,  and  extensive  submerged  plateaus  or  off-shore 
soundings,  such  as  might  have  existed  in  the  face  of  the 
ocean.  Here  the  change  of  level  was  very  great ;  for  within 
this  region  occur  the  seven  miles  of  Paleozoic  formations  (page 
141).  This  vast  thickness  indicates  that  while  there  were 
various  upward  and  downward  movements  over  this  Appala- 
chian region  through  Paleozoic  time,  the  downward  move- 
ments exceeded  the  upward  even  by  the  amount  just  stated. 
These  movements,  moreover,  were  in  progress  from  the  Pots- 
dam period  onward ;  the  formations  of  nearly  every  period  in 
the  series  exceed  8  to  10  times  the  thickness  they  have  over 
the  Interior  region. 

4.  Mountains  of  Paleozoic  origin.  —  The  mountains  in  Eastern 
North  America,  made  in  the  course  of  the  Paleozoic  ages, 
were  few.  Those  of  the  region  south  of  Lake  Superior  about 
Keweenaw  Point,  and  to  the  west,  probably  rose  during  the 
Canadian  period,  the  second  of  the  Lower  Silurian.  The 
Green  Mountain  region  became  dry  land  after  the  close  of  the 


146  PALEOZOIC   TIME. 

Lower  Silurian  (page  90) ;  but  there  is  no  reason  to  believe 
that  it  was  at  its  present  level,  for  the  Hudson  River  Valley 
east  of  Hudson,  and  part  or  all  of  the  Connecticut  Valley,  was 
beneath  the  ocean,  and  became  covered  by  crinoidal  and  coral 
reefs  and  other  formations  during  the  Lower  Helderberg  era, 
and  perhaps  also  during  the  early  Devonian.  The  Devonian 
and  other  beds  of  the  vicinity  of  Gaspe,  and  of  Nova  Scotia 
and  New  Brunswick,  were  raised  into  ridges  before  the  Car- 
boniferous age  began,  mountain-making  having  gone  forward 
in  this  Atlantic-border  region  after  the  close  of  the  Devonian. 
But  the  larger  part  of  the  continental  area  remained  without 
mountains.  The  Eocky  chain  had  only  some  ridges  as  isl- 
ands in  the  seas,  and  the  Appalachians  south  of  New  England 
were  yet  to  be  made. 

5.  Rivers ;  Lakes.  —  The  depression  between  the  New  York 
and  the  Canada  Archaean,  dating  from  Archaean  time,  was 
the  first  indication  of  a  future  St.  Lawrence  channel.  It  con- 
tinued to  be  an  arm  of  the  sea,  or  deep  bay,  through  the  Si- 
lurian, and  underwent  a  great  amount  of  subsidence  as  it 
received  its  thick  formations.  After  the  Silurian  age  marine 
strata  ceased  to  form,  indicating  thereby  that  the  sea  had  re- 
tired ;  and  fresh  waters,  derived  from  the  Archaean  heights  of 
Canada  and  New  York,  probably  began  their  flow  along  its 
upper  portion,  and  emptied  into  the  St.  Lawrence  Gulf  of  the 
time  not  far  below  Montreal. 

.  The  raising  of  New  York  State  out  of  water  at  the  close 
of  the  Devonian  suggests  that  from  that  time  the  Hudson 
Valley  was  a  stream  of  fresh  water.  The  valley  itself,  and 
its  continuation  north  as  the  Champlain  Valley,  date 
from  the  close  of  the  Lower  Silurian,  if  not  from  the  Ar- 
chaean. 

The  Mississippi  and  its  tributaries,  east  and  west,  were  not 
in  existence  in  the  Paleozoic  ages.  In  the  intervals  of  Car- 
boniferous verdure,  when  the  continent  was  emerged,  the 
Ohio  and  Mississippi  basin  were  regions  of  great  marshes, 
lakes,  and  bayous,  and  not  of  great  rivers ;  for  rivers  could 


GENERAL  OBSERVATIONS.  147 

not  exist  without  a  head  of  high  land  to  supply  water  and 
give  it  a  flow. 

Over  portions  of  Lake  Superior  there  were  extensive  rock- 
deposits  and  igneous  eruptions  in  part  of  the  Canadian  period ; 
and  the  thick  accumulations  show  that  deep  subsidences  were 
then  in  progress  there,  as  also  in  the  region  of  the  St.  Law- 
rence ;  so  that  we  may  infer  that  the  basin  of  this  great  lake 
was  already  in  process  of  formation  before  the  Lower  Silurian 
closed.  The  extent  and  position  of  the  great  Michigan  bay 
through  the  Silurian  and  Devonian  ages  and  much  of  the 
Carboniferous,  as  mentioned  on  pages  99, 138,  show  that  Lakes 
Erie,  Huron,  and  Michigan  were  then  within  the  limits  of 
this  bay.  Whether  deeper  or  not  than  other  portions  of  the 
bay,  is  not  known. 

Thus,  Geology  studies  the  Geography  of  the  Paleozoic  ages, 
and  traces  North  America  through  its  successive  stages  of 
growth. 

4.  Climate.  —  No  evidence   has   been  found  through   the 
Paleozoic  records  of  any  marked  difference  of  temperature 
between  the  zones.     In  the  Carboniferous  age  the  Arctic-seas 
had  their  Corals  and  Brachiopods,  and  the  Arctic  lands  their 
forests  and  marshes  under  dense  foliage,  no  less  than  those  of 
America  and  Europe.     The  facts  on  this  subject  are  stated  on 
page  136. 

5.  Life.  —  7.  Appearance  and  disappearance  of  species.  — With 
the  beginning  and  progress  of  each  formation  in  the  series, 
new  species  appeared,  and  the  old  ones  more  or  less  com- 
pletely disappeared.     Such  changes  in  the  life  occurred  in 
connection  even  with  the  minor  transitions  in  the  rock-for- 
mations, as  in  that  from  a  bed  of  shale  to  sandstone  or  to 
limestone,  and  the  reverse.     Thus,  through  the  ages,  life  and 
death  were  in  concurrent  progress. 

2.  Beginning  and  ending  of  genera,  families,  and  higher  groups. 
—  The  following  table  of  the  tribe  of  Trilobites  illustrates  the 
progress  which  took  place  in  this  group  and  exemplifies  the 
general  fact  with  regard  to  other  tribes  :  — 


148 


PALEOZOIC  TIME. 


Trilobites 

Paradoxides. 

Bathyurus 

Asaphus,  Remopleurides ... 


Calymene,  Ampyx,   Illsenus,   Acidaspis, 
and  Ceraurus 

Homalonotus  and  Lichas. 

Phillipsui,  Griffithides 


The  vertical  columns  correspond  to  the  Lower  and  Upper 
Silurian,  the  Devonian,  and  the  Carboniferous.  The  left- 
hand  column  under  Lower  Silurian  corresponds  to  the  first, 
or  Primordial  period ;  and  the  three  columns  under  the  Car- 
boniferous, to  the  Subcarboniferous,  Carboniferous,  and  Per- 
mian periods  of  the  age.  Opposite  TRILOBITES,  the  black  area 
shows  that  the  tribe  began  with  the  beginning  of  the  Paleo- 
zoic and  continued  nearly  to  its  end.  Next  there  is  the  name 
of  a  genus  which  existed  only  in  the  Primordial  period,  it 
having  then  many  species,  but  none  afterward ;  with  it  there 
were  other  genera  which  had  species  also  in  the  later  part  of 
the  Lower  Silurian.  Then  there  is  a  genus,  Bathyurus,  which 
continued  from  the  Primordial  through  the  Lower  Silurian. 
Then,  others  confined  to  the  rest  of  the  Lower  Silurian ;  others 
that  passed  into  the  Upper  Silurian,  then  to  become  extinct ; 
others  that  continued  into  the  Devonian;  and  two  genera 
confined  to  the  Carboniferous. 

In  a  similar  manner  the  genera  and  families  of  Brachiopods 
began  at  different  periods  or  epochs,  and  continued  on  for  a 
while,  to  become,  in  general,  extinct.  Many  genera  ended  in 
the  course  of  the  Paleozoic  and  at  its  close ;  only  a  few  con- 
tinued into  later  periods. 


GENERAL   OBSERVATIONS.  149 

3.  Special  Paleozoic  peculiarities  of  the  Life.  — The  following 
facts  show  in  what  respects  the  life  of  the  Paleozoic  ages  was 
peculiarly  ancient :  — 

a.  Not  only  are  the  species  all  extinct,  but  almost  every 
genus.     Fifteen  or  sixteen  of  the  genera  which  existed  in  the 
course  of  the  Paleozoic  have  living  species ;  and  all  these  are 
Molluscan. 

b.  Among  Eadiates,  the  Polyps  were  largely  of  the  tribe  of 
Cyathophylloid  corals,  which  is  almost  exclusively  ancient  or 
Paleozoic.     The  Echinoderms  were  mostly  Crinoids,  and  these 
were  in  great  profusion.     Crinoids  were  far  less  abundant, 
and  of  different  genera,  in  the  Mesozoic ;  and  now,  few  exist. 

c.  Among  Mollusks,  Brachiopods  were  exceedingly  abun- 
dant :  their  fossil  shells  far  outweigh  those  of  all  other  Mol- 
lusks.    But  in  the  Mesozoic  they  were  much  less  numerous 
than  other   Mollusks;   and  at   the   present  time  the  group 
is  nearly  extinct.     The  Cephalopods  were  represented  very 
largely  by  Orthocerata,  but  few  species  of  which  existed  in 
the  early  Mesozoic,  and  none  afterward. 

d.  Among  Articulates,  Trilobites  were  the  most  common 
Crustaceans,  —  a  group  exclusively  Paleozoic. 

e.  Among  Vertebrates,  the  Devonian  Fishes  were  either 
Ganoids,  Placoderms,  or  Selachians,  and  the  Ganoids  had  verte- 
Irated  tails.     Of  this  kind  of  Ganoids,  but  few  species  lived 
in  the  first  period  of  the  Mesozoic ;  and  the  whole  group  of 
Ganoids  is  now  nearly  extinct.     Of  the  Selachians,  a  large 
proportion  were  Cestracionts,  —  a  tribe  common  in  the  Meso- 
zoic, but  now  nearly  extinct. 

/.  Among  terrestrial  Plants,  there  were  Lepidodendrids, 
Sigillarids,  Catamites  in  great  profusion,  mating,  with  Conifers 
and  Ferns,  the  forests  and  jungles  of  the  Carboniferous  and 
later  Devonian :  no  Lepidodendrid  or  Sigillarid  existed  after- 
ward, and  the  Calamites  ended  in  the  Mesozoic. 

Thus,  the  Paleozoic  or  ancient  aspect  of  the  animal  life  was 
produced  through  the  great  predominance  of  Brachiopods,  Cri- 
noids, Cyathophylloid  Corals,  Orthocerata,  Trilobites,  and  verte- 


150  PALEOZOIC  TIME. 

brated-tailed  Ganoids ;  and  that  of  the  plants  over  the  land, 
through  the  Lepidodendrids,  Sigillarids,  and  Calamites,  along 
with  the  Ferns  and  Conifers.  In  addition  to  this  should  be 
mentioned  the  absence  of  Angiosperms  and  Palms  among 
Plants ;  the  absence  of  Teliost  Fishes,  and  of  Birds  and  Mam- 
mals, among  Vertebrates ;  and  of  nearly  all  modern  tribes  of 
genera  among  Radiates,  Mollusks,  and  Articulates. 

4.  Mesozoic  and  Modern  types  begun  in  Paleozoic  time.  —  The 
principal  Mesozoic  type  which  began  in  the  Paleozoic  was  the 
Reptilian.  But  besides  these  Reptiles  there  were  the  first  of 
the  Decapod  Crustaceans ;  the  first  of  Oysters ;  the  first  of  the 
great  tribe  of  Ammonites,  the  Goniatites  being  of  this  tribe ; 
the  first  of  Insects,  Spiders  and  Centipedes.  The  type  of  In- 
sects, or  terrestrial  Articulates,  belongs  eminently  to  modern 
time ;  for  it  probably  has  now  its  fullest  display. 

Thus,  while  .the  Paleozoic  ages  were  progressing,  and  the 
types  peculiar  to  them  were  passing  through  their  time  of 
greatest  expansion  in  numbers  and  perfection  of  structure, 
there  were  other  types  introduced  which  were  to  have  their 
culmination  in  a  future  age.  ...*-. 

DISTURBANCES   CLOSING  PALEOZOIC  TIME. 

L  General  quiet  of  the  Paleozoic  Ages.  —  The  long  ages  of 
the  Paleozoic  passed  with  but  few  and  comparatively  small 
disturbances  of  the  strata  of  Eastern  North  America.  There 
were  some  early  permanent  uplifts  in  the  Lake  Superior 
region,  during  the  Lower  Silurian;  again,  after  the  Lower 
Silurian,  the  Green  Mountains  were  made ;  and  again,  after 
the  close  of  the  Devonian,  there  were  disturbances  and  upturn- 
ings  in  Eastern  New  Brunswick,  part  of  Nova  Scotia,  and  East- 
ern Canada  by  Gaspe  near  St.  Lawrence  Bay.  Besides  these 
changes  there  was,  through  the  ages,  a  gradual  increase  on 
the  north  in  the  amount  of  dry  land ;  and  through  parts  of 
all  the  periods,  over  a  large  part  of  the  continent,  slow  oscil- 
lations were  in  progress,  varying  the  water-level  and  favoring 


APPALACHIAN   REVOLUTION.  151 

the  increasing  thickness  of  the  rocks,  and  their  successive 
variations  as  to  kind  and  extent.  But  these  movements  of 
the  earth's  crust  were  exceedingly  slow,  —  probably  less  than 
a  foot  a  century.  There  may  have  been  many  occasional 
quakings  of  the  earth,  —  even  exceeding  the  heaviest  of 
modern  earthquakes.  There  may  have  been  at  times  sudden 
risings  or  sinkings  of  portions  of  the  continental  crust.  But 
the  condition  of  the  strata  of  the  interior  of  the  continent, 
and  of  the  Appalachian  region  south  of  the  Green  Mountains, 
indicates  that  general  quiet  prevailed  through  the  long  Paleo- 
zoic ages. 

2.  The  Appalachian  the  region  of  greatest  change  of  level 
through  the  Paleozoic.  —  The  region  of  greatest  movement  dur- 
ing these  ages  was  the  Appalachian.     For  it  has  been  shown 
that  the  oscillations  which  there  took  place  resulted  in  sub- 
sidences of  one  or  more  thousand  feet  with  nearly  every  period 
of  the  Paleozoic.     In  the  Green  Mountain  portion  the  oscilla- 
tions ceased  after  the  close  of  the  Lower  Silurian  era ;  but  not 
until  the  subsidence  there  had  reached  probably  20,000  feet : 
and  in  Pennsylvania  and  Virginia  they  continued  through  a 
large  part  of  the  Carboniferous  age,  until  the  sinking  amounted 
to  35,000  or  40,000  feet.     But  this  sinking  was  quiet  in  its 
progress,  as  is  proved  by  the  regularity  in  the  series  of  strata. 

The  thickness  of  the  coal-beds  indicates  that  the  coal-plant 
marshes  were  long  undisturbed,  and  therefore  that  long  periods 
passed  without  appreciable  movement. 

3.  Approach  of  the  epoch  of  Appalachian  revolution.  —  The 
era  of  comparative  quiet  alluded  to  came  gradually  to  a  close 
as  the  Carboniferous  age  was  terminating,  and  an  epoch  of 
upturning  and  mountain-making  began.     There  are  mountains 
to  testify  to  this  both  in  Europe  and  America. 

In  Eastern  North  America  the  disturbances  affected  Nova 
Scotia  and  the  coal  area  of  Ehode  Island  and  Southeastern 
Massachusetts  ;  and,  with  far  grander  results,  the  Appalachian 
region  and  Atlantic  border  from  Southern  New  York  to  Ala- 
bama. The  Appalachian  mountains  are  a  part  of  the  result, 


152  CLOSE  OF  PALEOZOIC  TIME. 

and  hence  the  epoch  is  appropriately  styled  the  epoch  of  the 
Appalachian  revolution.  The  region  in  Eastern  America  of 
the  deepest  Paleozoic  subsidence  and  of  the  thickest  accumu- 
lation of  Paleozoic  rocks,  that  is,  the  Appalachian,  was  now  the 
region  of  the  profoundest  disturbances  and  the  greatest  uplifts. 
4.  Effects  of  the  disturbances.  —  The  following  are  among 
the  effects  of  the  disturbances  along  the  Appalachian  region 
and  Atlantic  border :  — 

1.  Strata  were  upraised  and  flexed  into  great  folds,  some 
of  the  folds  a  score  or  more  of  miles  in  span. 

2.  Deep   fissures  of  the  earth's   crust  were   opened,  and 
faults  innumerable  were  produced,  some  of  them  of  10,000 
to  20,000  feet. 

3.  Eocks  were  consolidated;  and  over  some  parts  sand- 
stones and  shales  were  crystallized  into  gneiss,  mica-schist, 
and  other  related  rocks,  and  limestone  into  architectural  and 
statuary  marble. 

4.  Bituminous  coal  was  turned  into  anthracite  in   Penn- 
sylvania and  Ehode  Island. 

5.  In  the  end,. the  Appalachian  mountains  were  made.      •; 
5.  Evidence  of  the  flexures,  uplifts,  and  metamorphism. — 

The  evidence  that  the  rocks  of  the  Appalachian  region  and 
Atlantic  border  were  flexed,  uplifted,  faulted,  and  -otherwise 
changed  from  their  original  condition,  is  as  follows  :  — 

The  Coal-measures  and  other  Paleozoic  strata,  though 
originally  spread  out  in  horizontal  beds,  are  now  in  an  uplifted 
and  flexed  or  folded  condition  ;  and  they  are  so  involved  to- 

Fig.  250. 


Section  of  the  Coal-measures  near  Nesquehoning,  Pennsylvania. 

gether  in  one  system  of  flexures  and  uplifts  that  the  whole 
must  have  been  the  result  of  one  system  of  movements. 
Figs.  250  -  253  illustrate  this. 


APPALACHIAN  REVOLUTION. 


Fig.  250  shows  the  condition  of  the  Anthracite  coal-beds 
of  Mauch  Chunk  in  Pennsylvania.     Some  of  the  upturned 


Fig.  251. 


Section  on  the  Schuylkill,  Pennsylvania  ;  P.,  Pottsville  on  the  Coal-measures ;  2,  Calciferous 
formation  ;  3,  Trenton  ;  4,  Hudson  River ;  5,  Oneida  and  Niagara ;  7,  Lower  Helderberg ; 
8,  10,  11,  Devonian ;  12,  13,  Subcarboniferous  ;  14,  Carboniferous,  or  Coal-measures. 

beds,  as  is  seen,  stand  nearly  vertical.  Fig.  251  is  from 
another  locality  near  Pottsville  in  the  same  State.  The  coal- 
beds  are  the  upper  ones  numbered  14 ;  the  rest  are  the  beds  of 
the  Upper  and  Lower  Silurian  (2  to  7) ;  the  Devonian  (8,  10, 
11)  and  Subcarboniferous  (12,  13). 


Fig.  252  was  taken  from 


Fig.  252. 


Section  from  the  Great  North  to  the  Little  North  Mountain  through  Bore  Springs,  Virginia  ; 
t,  t,  position  of  thermal  springs ;  11,  Calciferous  formation  ;  in,  Trenton  ;  iv,  Hudson 
River;  v,  Oneida;  vi,  Clinton  and  Lower  Helderberg,  vu,  Oriskany  Sandstone  and 
Cauda-Galli  Grit. 

the  vicinity  of  Bore  Springs,  in  Virginia,  and  includes  Silurian 
and  Devonian  beds :  it  shows  well  the  folded  character  of  the 


Fig.  253. 


m 


Section  of  the  Paleozoic  formations  of  the  Appalachians  in  Southern  Virginia,  between 
Walker's  Mt.  and  the  Peak  Hills  (near  Peak  Creek  Valley) :  F,  fault ;  a,  Lower  Silurian 
limestone  ;  &,  Upper  Silurian  ;  c,  Devonian ;  d,  Subcarboniferous,  with  coal-beds. 

rocks.     Fig.  253  represents  one  of  the  great  faults  in  South- 
ern Virginia  (between  Walker's  Mountain  and  Peak  Hills) ; 


154  CLOSE   OF  PALEOZOIC   TIME. 

the  break  is  at  F,  and  the  rocks  on  the  left  were  shoved 
up  along  the  sloping  fracture  until  a  Lower  Silurian  lime- 
stone (a)  was  on  a  level  with  the  Subcarboniferous  formation 
(cQ,  a  fault  of  more  than  10,000  feet.  Such  examples  are 
in  great  numbers  throughout  the  Appalachians.  In  many 
of  the  transverse  valleys  the  curves  may  be  traced  for  scores 
of  miles. 

As  shown  in  the  above  sections  (Figs.  250-253),  the  folds, 
instead  of  remaining  in  regular  rounded  ridges  with  even 
synclinal  valleys  between,  such  as  the  flexing  of  the  strata 
might  make,  have  been  to  a  great  extent  worn  away,  or  mod- 
elled into  new  ridges  and  valleys,  by  the  action  of  waters 
during  subsequent  time ;  and  often  what  was  the  top  of  a  fold 
is  now  the  bottom  of  a  valley,  because  the  folds  would  be 
most  broken  where  most  abruptly  bent,  —  that  is,  along  the 
axes  of  upward  flexure,  —  and  hence  would  be  most  liable  in 
these  parts  to  be  cut  away  or  gorged  out  by  any  denuding 
causes.  The  figures  on  page  43  illustrate  still  further  the 
condition  of  folded  strata  before  and  after  denudation.  Some 
of  the  Appalachian  folds  were  probably  20,000  feet  in  heigtit 
above  the  present  level  of  the  ocean,  or  would  have  had  this 
height  if  they  had  remained  unbroken,  while  in  fact  the 
loftiest  summits  now  are  less  than  5,000  feet,  and  few  exceed 
3,000  feet. 

Over  New  England  there  are  similar  flexures.  Those  of 
the  Rhode  Island  coal-formation  are  very  abrupt,  and  full  of 
faults,  the  coal-beds  being  much  broken  and  displaced. 

6.  General  truths  with  regard  to  the  results. — The  follow- 
ing are  some  of  the  general  truths  connected  with  the  uplifts 
and  metamorphism  :  — 

1.  The  courses  of  the  flexures  and  of  the  outcrops  or 
strike,  and  those  of  the  great  faults,  are  approximately  north- 
east, or  parallel  to  the  Atlantic  border.  There  is  a  bend 
eastward  in  Pennsylvania  corresponding  with  the  eastward 
bend  of  the  southern  coast  of  New  England,  and  then  a  change 
to  the  northward  in  New  England. 


APPALACHIAN   REVOLUTION.  155 

2.  The  folds  have  their  steepest  slope  toward  the  northwest, 
or  away  from  the  ocean.     If  Fig.  41  (page  43)  represent  one 
of  the  folds,  the  left  would  be  the  ocean  side,  or  that  to  the 
southeast,  and  the  right  the  landward  side,  or  that  to  the 
northwest. 

3.  The  flexures  are  most  numerous  and  most  crowded  on 
that  side  of  the  Appalachian  region  which  is  toward  the  ocean, 
and  diminish  westward.     There  is  seldom,  however,  a  gradual 
dying  out  westward,  the  region  of  disturbance  being  often 
bounded  on  the  west  by  one  or  more  of  the  great  fractures 
and  faults,  as  in  Eastern  Tennessee  and  along  the  valley  of 
the  Hudson. 

4.  The  consolidation  and  metamorphism  of  the  strata  are 
more  extensive  and  complete  to  the  eastward  (or  toward  the 
ocean)  than  to  the  westward. 

5.  The  change  of  bituminous  coal  to  anthracite,  by  the 
expulsion  of  volatile  ingredients,  was  most  complete  where 
the  disturbances  were  greatest,  —  that  is,  in  the  more  eastern 
portions  of  the  coal  areas.     The  anthracite  region  of  Penn- 
sylvania (see  map,  p.  116)  owes  its  broken  character  partly 
to  the  uplifts  and  partly  to  denudation.     To  the  westward 
the  coal  is  first  semi-bituminous,  and  then,  as  at  Pittsburg, 
true   bituminous.     In  Ehode   Island,  where   the   associated 
rocks  are  partly  true  metamorphic  or  crystalline  rocks  and  the 
disturbances  are  very  great,  the  coal  is  an  extremely  hard 
anthracite,  and  in  some  places  is  altered  to  graphite,  —  an 
effect  which  may  be  produced  in  ordinary  coal  by  the  heat 
of  a  furnace. 

7.  Conclusions,  —  These  facts  lead  to  the  following  conclu- 
sions :  — 

1.  The  movement  producing  these  vast  results  was  due  to 
lateral  pressure,  the  folding  having  taken  place  just  as  it 
might  in  paper  or  cloth  under  a  lateral  or  pushing  movement. 

2.  The  pressure  was  exerted  at  right  angles  to  the  courses 
of  the  folds,  as  is  the  case  when  paper  is  folded  in  the  manner 
mentioned. 


156  CLOSE   OF  PALEOZOIC   TIME. 

3.  The  pressure  was  exerted  from  the  ocean  side  of  the 
Appalachians ;  for  the  results  in  foldings  and  metamorphism 
are  most  marked  toward  the  ocean. 

4.  The  force  was  vast  in  amount. 

5.  The  force  was  slow  in  action  and  long  continued,  —  and 
not  abrupt  or  paroxysmal  as  when  a  wave  or  series  of  waves 
is  thrown  up  by  an  earthquake  shock  on  the  surface  of  an 
ocean.     For  the  strata  were  not  reduced  by  it  to  a  state  of 
chaos,  but  retain  their  stratification,  and  show  comparatively 
little  confusion,  even  in  the  regions  of  greatest  disturbance 
and  alteration. 

6.  The  action  of  the  force  was  attended  by  the  production 
of  heat.     For  without  some  heat  above  the  ordinary  tempera- 
ture, it  is  not  possible  to  account  for  the  consolidation  and 
crystallization  of  the  rocks. 

7.  The   history   of  the   Appalachian   Mountains   extends 
through  all   the  geological  ages  from  the  Archaean  onward. 
During  the  Silurian,  Devonian,  and  Carboniferous  ages  the 
formations  were  accumulating  to  a  great  thickness,  while  a 
slow  subsidence  was  in  progress.     When  the  Carboniferous 
age  was  closing,  and  the  subsidence  had  reached  a  depth  of 
several  miles,  there  were  other  movements,  producing  flexures 
of  the  strata,  uplifts,  faults,  consolidation,  and  metamorphism, 
and  ending  in  the  making  of  the  mountains.     And  finally, 
during  these  upliftings,  moving  waters  commenced  the  work 
of  denudation,  which  has  been  continued  to  the  present  time. 

8.  Disturbances  on  other  continents. — The  amount  of  con- 
temporaneous mountain-making  over  the  globe  at  this  epoch 
has  not  yet  been  clearly  made  out.     Enough  is  known  to  ren- 
der it  probable  that  the  Ural  Mountains,  with  their  veins  of 
gold  and  platinum,  were  made  at  the  same  time  with  the  Ap- 
palachians, and  that  uplifts  and  metamorphism  also  occurred 
in  other  parts  of  Europe,  and  in  Great  Britain.     Murchison 
states  that  the  close  of  the  Carboniferous  period  was  specially 
marked  by  disturbances  and  uplifts ;  that  it  was  then  "  that 
the  coal  strata  and  their  antecedent  formations  were  very 


MESOZOIC  TIME.  157 

generally  broken  up,  and  thrown,  by  grand  upheavals,  into 
separate  basins,  which  were  fractured  by  numberless  power- 
ful dislocations." 

The  epoch  of  the  Appalachian  revolution  was,  then,  a  grand 
epoch  for  the  world.  The  extermination  of  life  which  took 
place  at  the  time  was  one  of  the  most  extensive  in  all 
geological  history,  and  must  have  been  a  consequence  of  the 
great  physical  changes  progressing  over  the  earth's  surface. 
But  it  cannot  be  affirmed  that  the  extermination  was  univer- 
sal, although  no  fossils  of  the  Carboniferous  formation  occur  in 
later  rocks ;  for  these  strata,  as  they  are  confined  to  portions 
of  the  continental  seas,  testify  only  as  to  changes  and  de- 
structions throughout  those  seas,  and  not  respecting  the  life 
existing  elsewhere. 


III.  —  MESOZOIC  TIME. 

1.  Ages.  —  Mesozoic  or  mediaeval  time,  in  Geological  his- 
tory, comprises  but  one  age,  —  the  EEPTILIAN.     In  the  course 
of  it  the  class  of  Eeptiles  passed  its  culmination ;  —  that  is, 
its  species  increased  in  numbers,  size,  and  diversity  of  forms, 
until  they  vastly  exceeded  in  each  of  these  respects  the  Hep- 
tiles  of  either  earlier  or  later  time. 

2.  Area  of  progress  in  rock-making.  —  The  area  of  rock- 
making  in  North  America,  during  Mesozoic  time,  was  some- 
what different  from  what  it  was  in  Paleozoic.     Then,  nearly 
the  whole  continent,  outside  of  the  northern  Archaean  area, 
was  receiving  its  successive  formations ;  and  the  three  great 
regions  were  the  Eastern  border,   the  Appalachian,  and  the 
Interior    Continental.     By  the   close    of  Paleozoic   time  the 
Appalachian  region  and  the  Interior  east  of  the  Mississippi, 
excepting  its  southern  portion,  had  become  part  of  the  dry 
land  of  the  continent,  as  is  shown  by  the  absence  of  marine 
strata  of  later  date.     The  great  areas  of  progress  were  conse- 


158  MESOZOIC   TIME.  —  REPTILIAN  AGE. 

quently  changed,  and  became  (1)  the  Atlantic  border,  (2) 
the  Gulf  border,  and  (3)  the  Western  Interior,  or  region  west 
of  the  Mississippi.  In  other  words,  the  continent,  from  the 
Mesozoic  onward,  until  the  close  of  the  Tertiary  period  in  the 
Cenozoic,  was  receiving  its  new  marine  formations  along  its 
borders,  and  in  extensive  areas  over  the  part  of  the  Interior 
region  embraced  by  the  Summit  region  and  slopes  of  the 
Rocky  Mountains. 

These  three  regions  are  continuous  with  one  another,  the 
Atlantic  connecting  with  the  Gulf  border  region  on  the  south, 
and  the  Gulf  border  region  passing  northwestward  into  the 
Western  Interior  or  Rocky  Mountain  region  and  Pacific 
border. 

In  Europe  no  analogous  change  can  be  distinguished ;  for 
the  continent  was,  from  the  first,  an  archipelago,  and  it  con- 
tinued to  bear  this  geographical  character,  though  with  an 
increasing  prevalence  of  dry  land,  until  the  Cenozoic  era  had 
half  passed.  Western  England  then  stood  as  three  or  four 
islands  above  the  sea  (the  area  marked  as  covered  by  Paleo- 
zoic rocks  on  the  map,  page  118) ;  and  the  area  of  future  rock- 
making  was  mainly  confined  to  the  intervals  between  these 
islands  and  to  the  submerged  area  on  the  east  and  southeast. 
It  is  probable  that  this  area  and  a  portion  of  Northeastern 
France  were,  geologically,  part  of  a  large  German-Ocean  basin. 

REPTILIAN  AGE. 

Periods.  —  The  Reptilian  Age  includes  three  periods  :  — 
7.  Tn'assic :  named  from  the  Latin  tria,  three,  in  allusion  to 
the  fact  that  the  rocks  of  the  period  in  Germany  consist  of 
three  separate  groups  of  strata.  This  is  a  local  subdivision, 
not  characterizing  the  rocks  in  Britain  or  in  most  other  parts 
of  Europe. 

2.  Jurassic:  named  from  the  Jura  Mountains,  situated  on 
the  eastern  border  of  France,  between  France  and  Switzerland, 
where  rocks  of  the  period  occur. 


TRIASSIC   AND   JURASSIC  PERIODS.  159 

3.  Cretaceous :  named  from  the  Latin  creta,  chalk,  the  chalk- 
beds  of  Britain  and  Europe  being  included  in  the  Cretaceous 
formation. 

1.  Triassic  and  Jurassic  Periods. 
I.  Rocks:  Kinds  and  Distribution. 

The  American  rocks  of  the  Triassic  period  have  not  yet 
been  separated  from  those  of  the  Jurassic,  except  in  the  re- 
gion west  of  the  Mississippi. 

In  the  Atlantic-border  region  these  rocks  occupy  narrow 
ranges  of  country  parallel  with  the  Appalachian  chain,  fol- 
lowing its  varying  courses.  One  of  these  ranges  occupies  the 
valley  of  the  Connecticut  between  Northern  Massachusetts 
and  New  Haven  on  Long  Island  Sound,  and  runs  parallel 
with  the  Green  Mountains:  it  has  a  length  of  about  110 
miles.  Another  —  the  longest  of  them  —  commences  at  the 
north  extremity  of  the  Palisades,  on  the  west  bank  of  the 
Hudson  River,  and  stretches  southwestward  through  New 
Jersey,  Pennsylvania  (here  bending  much  to  the  westward, 
like  the  Appalachians  of  the  State,  as  shown  in  the  map  on 
page  116),  and  reaching  far  into  the  State  of  Virginia. 
Another  stretches  —  almost  in  the  line  of  the  last  —  through 
North  Carolina.  There  is  another  along  Western  Nova  Scotia. 
These,  and  some  other  smaller  areas,  are  indicated  on  the  map 
on  page  69  by  an  oblique  lining  in  which  the  lines  run  from 
the  right  above  to  the  left  below. 

The  rocks  are  mainly  sandstones  and  conglomerates,  but 
include  some  considerable  beds  of  shale,  and  in  a  few  places 
impure  limestone.  The  sandstones  are  generally  red  or 
brownish-red.  The  freestone  of  Portland,  near  Middletown 
in  Connecticut,  and  of  the  vicinity  of  Newark  in  New  Jer- 
sey, are  from  this  formation.  The  pebbles  and  sand  of  the 
beds  were  derived  mainly  from  metamorphic  rocks  alongside 
of  the  regions  in  which  they  lie ;  and  from  some  of  the 
coarser  layers  large  stones  of  granite,  gneiss,  and  mica-schist 


160  MESOZOIC   TIME.  — REPTILIAN  AGE. 

may  be  taken.  The  strata  overlie  directly,  but  unconform- 
ably,  these  inetamorphic  rocks.  Near  Eichmond  in  Virginia 
and  in  North  Carolina  there  are  valuable  beds  of  bituminous 
coal. 

The  several  ranges  of  this  sandstone  formation  are  remark- 
able for  the  great  number  of  trap  dikes  and  trap  ridges  inter- 
secting them  (page  30).  Mount  Holyoke  in  Massachusetts, 
East  and  West  Eocks  near  New  Haven  in  Connecticut,  and 
the  Palisades  on  the  Hudson  are  a  few  examples  of  these 
trap  ridges.  Trap  is  an  igneous  rock,  one  that  was  ejected  in 
a  melted  state  from  a  deep-seated  source  of  fire,  through  fis- 
sures made  by  a  fracturing  of  the  earth's  crust.  The  dikes 
and  ridges  are  exceedingly  numerous,  and  have  the  same  gen- 
eral course  with  the  sandstone  ranges.  They  are  so  associated 
with  the  sandstone  formation  that  there  must  have  been 
some  connection  in  origin  between  the  water-made  and  the 
fire-made  rocks.  The  proofs  that  the  trap  came  up  through 
the  fissures  in  a  melted  state  are  abundant ;  for  the  wall-rock 
of  the  fissures  is  often  baked  so  as  to  be  very  hard,  and  is 
sometimes  filled  with  crystallizations,  as  of  epidote,  tourma- 
line, garnet,  hematite,  etc.,  evidently  due  to  the  heat. 

West  of  the  Mississippi,  in  the  Western  Interior  region 
southwest  of  Southern  Kansas,  there  is  a  sandstone  formation, 
containing  much  gypsum  (and  hence  called  the  gypsiferous 
formation),  but  barren  of  fossils,  except  an  occasional  frag- 
ment or  trunk  of  fossil  wood,  which  is  regarded  as  Triassic. 
Triassic  beds  occur  also  in  Colorado  and  New  Mexico,  Utah 
and  Nevada.  Along  with  Jurassic  strata  they  enter  into  the 
constitution  of  the  Elk  and  Wahsatch  mountains,  and  the 
Sierra  Nevada.  These  western  Jurassic  beds  in  many  places 
contain  fossils,  but  only  rarely  so  the  Triassic. 

In  the  vicinity  of  the  Black  Hills,  in  the  region  of  the 
Upper  Missouri,  there  are  some  beds  of  impure  limestone  con- 
taining marine  fossils  which  are  true  Jurassic. 

In  Europe,  the  Triassic  rocks  of  Eastern  France  and  Ger- 
many, east  and  west  of  the  Ehine,  consist  of  a  shell  limestone 


TRIASSIC  AND  JURASSIC  PERIODS.  161 

(called  in  German  Muschelkalk)  between  an  underlying  thick 
reddish  sandstone  (Bunter  Sandstein)  and  overlying  strata  of 
reddish  and  mottled  marlytes  and  sandstone  (Keuper  of  the 
Germans).  In  England  (see  No.  6  on  map,  page  118),  the 
formation  consists  of  reddish  sandstone  and  marlytes;  it  is 
mostly  confined  to  a  region  running  north-northwest  just  east 
of  the  Paleozoic  areas,  and  to  an  extension  of  this  region 
westward  to  Liverpool  bay  (or  over  the  interval  between  the 
two  main  areas)  and  up  the  west  coast. 

This  formation,  in  Europe,  contains  in  many  places  beds 
of  salt,  and  is  hence  often  called  the  Saliferous  group.  At 
Northwich  in  Cheshire,  in  England,  there  are  two  beds  of 
rock-salt,  90  to  100  feet  thick;  and  in  Europe  there  are  simi- 
lar beds  at  Vic  and  Dieuze  in  Prance,  and  at  Wurtemberg  in 
Germany. 

The  Jurassic  rocks  of  Britain  and  Europe  are  divided  into 
three  principal  groups  :  — 

1.  The  Liassic  (No.  7 a  on  map  of  England,  page  118),  con- 
sisting of  grayish  compact  limestone  strata,  called  Lias. 

2.  The  Oolytic  (No.  76  on  map,  page  118),  consisting  mostly 
of  whitish  and  grayish  limestones,  part  of  them  oolitic  (page 
25).     One  stratum,  near  the  middle  of  the  series,  is  a  coral- 
reef  limestone,  much  like  the  reef-rock  of  existing  coral  seas, 
though  different  in  species  of  coral.     Near  the  top  of  the  series 
there  are  some  local  beds  of  fresh-water  or  terrestrial  origin, 
in  what  is  called  the  Purbeck  group,  and  one  on  the  island 
of  Portland  is  named,  significantly,  the  Portland  dirt-bed.    The 
Solenhofen  lithographic  limestone  is  a  very  fine-grained  rock 
(thereby  fit  for  lithography),  of  the  age  of  the  Middle  Oolyte 
occurring  in  Pappenheim  in  Bavaria. 

3.  The  Wealden  (No.  8  on  the  map  of  England),  a  series 
of  beds  of  estuary  and  fresh-water  origin,  mostly  clay  and 
sand,  but  partly  of  limestone.     They  occur  in  Southeastern 
England.     They  are  named   Wealden  from  the  region  where 
first  studied,  called  the  Weald,  covering  parts  of  Kent,  Surrey, 
and  Sussex. 


162 


MESOZOIC   TIME.— REPTILIAN  AGE. 


2.    Life. 
1.    Plants. 

The  vegetation  of  the  Triassic  and  Jurassic  periods  included 
numerous  kinds  of  Ferns,  both  large  and  small,  Catamites  t  and 
Conifers,  and  so  far  resembled  that  of  the  Carboniferous  age. 
But  there  were  no  forests  or  jungles  of  Lepidodendrids  and 
Sigillarids.  Instead  of  these  Carboniferous  types,  a  group  of 
trees  and  shrubs  sparingly  represented  in  the  later  Carbon- 
iferous, that  of  the  Cycads,  was  eminently  characteristic  of 
the  Mesozoic  world.  This  group  has  now  but  few  living 

species,  and  among 

Fig-  254*  the    genera,    Cycas 

and  Zamia  are  those 
whose  names  are 
best  known.  The 
plants  have  the  as- 
pect of  Palms ;  and 

Fig.  255. 


CYCADS:  Fig.  254,  Cycas  circinalis(x  -j-^j)  j  255,  leaf  of  a  living  Zamia  (  x 


there  was,  therefore,  in  the  Mesozoic  forests  a  mingling  of 
palm-like  foliage  with  that  of  Conifers  (Spruce,  Cypress,  and 
the  like).  But  the  Cycads  are  not  true  Palms.  They  are 


TRIASSIC   AND   JURASSIC   PERIODS. 


163 


Fig.  256. 


Gymnosperms,  like  the  Conifers  both  in  the  structure  of  the 
wood  and  in  the  fruit.  The  resemblance  to  Palms  is  mainly  in 
the  cluster  of  great  leaves  at  the  sum- 
mit, and  in  the  appearance  of  the  exte- 
rior of  the  trunk.  Fig.  254  represents, 
much  reduced,  a  modern  Cycas,  and 
fig.  255  the  leaf  of  a  living  Zamia,  one 
twentieth  the  actual  length.  The  fossil 
remains  of  Cycads  are  either  their 
trunks  or  leaves.  A  fossil  species  from 
the  Portland  dirt-bed  is  represented  in 
fig.  256.  The  trunks  of  some  Cycads 
have  a  height  of  15  or  20  feet.  In 
one  important  respect  these  Cycads 
resemble  the  Ferns,  —  that  is,  in  the  unfolding  of  the  young 

Figs.  257-261. 


Stump  of  the  Cycad,  Mantellia 
(Cycadeoidea)      megalophylla 


Fig.  257,  Podozamites  lanceolatus  ;  258,  Pterophyllum  graminioides  ;  259,  Clathropteris  reo- 
tiusculus ;  260,  Pecopteris  (Lepidopteris)  Stuttgartensis ;  261  a,  Cyclopteris  linnseifolia. 


164  MESOZOIC  TIME.  — REPTILIAN  AGE. 

leaf,  — the  leaf  being  at  first  rolled  up  into  a  coil,  and  grad- 
ually unrolling  as  it  expands.  The  Cycads  thus  combine 
peculiarities  of  three  orders  of  plants,  —  Ferns,  Palms,  and 
Conifers,  —  and  are  examples,  therefore,  of  what  are  called 
comprehensive  types. 

Fossil  plants  are  common  in  the  coal-regions  of  Eichmond, 
Virginia,  and  in  North  Carolina,  and  occur  also  in  other 
localities.  Figs.  256,  257  are  parts  of  the  leaves  of  two 
species  of  Cycads,  from  North  Carolina.  Figs.  258  to  260 
represent  a  few  of  the  ferns :  Fig.  258,  a  Clathropteris,  from 
East  Hampton,  Mass. ;  Fig.  259,  a  Pecopteris,  from  Eichmond, 
Va.,  and  the  Trias  of  Europe;  Fig.  260,  a  Cydopteris,  from 
Eichmond,  Ya.  Large  cones  of  firs  have  also  been  found. 
Several  of  the  American  plants  are  identical  in  species  with 
those  of  the  European  Triassic,  and  a  few  nearer  to  Jurassic 
forms. 

2.  Animals. 
a.   American. 

The  American  beds  of  the  Atlantic  border  region  are  re- 
markable for  the  absence  of  true  marine  life :  all  the  species 
appear  to  be  either  those  of  brackish  water,  or  of  fresh  water, 
or  of  the  land. 

1.  Radiates  and  Mollusks.  —  In  the  beds  of  the  Atlantic 
border  Eadiates  are  unknown ;  and  the  remains  of  Mollusks 
are  of  doubtful  character.     The  Jurassic  beds  of  the  Eocky 
Mountain  region  and  its  western  borders  contain  many  spe- 
cies, and  the  Triassic  of  California  a  few. 

2.  Articulates.  —  The   shells  of   Ostracoid  Crustaceans  are 
common  in  Pennsylvania,  Virginia,  and  North  Caro- 
lina, but  have  not  yet  been  found  in  New  England.  Fig.  261. 
Fig.  261  represents  one  of  the  little  shells  of  these 
bivalve  species,  called  an  Estheria.     It  was  long  sup- 
posed to  be  Molluscan.     The  Estherice  are  brackish- 
water  species. 

A  few  remains  of  Insects  have  been  found,  and,  what  is  more 
remarkable,  the  tracks  of  several  species.  These  tracks  were 


TRIASSIC  AND  JURASSIC  PERIODS. 


165 


Pigs.  262  -  264. 

263 


264 


It    N, 
\ 


A 
f\ 

f\ 


made  on  the  soft  mud,  probably  by  the  larves  of  the  Insects, 
for  certain  kinds  pass  their  larval  state  in  the  water.  Fig. 
262  represents  one  of  these  larves  found  in  shale  at  Turner's 
Falls  in  Massachusetts;  it  resembles,  according  to  Dr.  Le  Conte, 
the  larve  of  a  modern  Ephemera,  or  May-fly.  Figs.  263,  264 
are  the  tracks  of  Insects.  Pro- 
fessor Hitchcock  has  named 
nearly  30  species  of  tracks  of 
Insects  and  Crustaceans. 

3.  Vertebrates.  —  There  are 
evidences  of  the  existence  of 
Fishes,  Reptiles,  Mammals,  and 
probably  Birds.  With  the  ap- 
pearance of  the  last  two  types 
the  sub-kingdom  of  Vertebrates 
was  finally  represented  in  all  its  ARTICULATES.  —  Fig. 

classes  mediaeva  (  x  \\) ;  263,  264,  Tracks  of  Insects. 

The  Fishes  found  in  the  American  rocks  are  all  Ganoids, 
although  Selachian  remains  are  common  in  Europe.  Fig.  265 
represents  one  of  the  species,  reduced  one  half ;  the  tail  is  half 
vertebrated.  In  other  species  of  these  rocks  it  is  not  at  all 
vertebrated,  being  like  that  of  modern  Ganoids ;  and  in  them 
this  old  paleozoic  feature  of  the  Ganoids  is  finally  lost. 

Fig.  265. 


Pig.  265,  GANOID,  Catopterus  gracilis  (x  J);  a,  Scale  of  same,  natural  size. 

The  Eeptiles  of  the  era  are  known  to  us  partly  from  their 
fossil  bones,  and  partly  from  their  footprints.  The  footprints 
indicate  a  wonderful  varietv  as  to  form  and  size.  Bones  have 


166  MESOZOIC  TIME.  — REPTILIAN  AGE. 

been  found,  especially  in  Pennsylvania,  North  Carolina,  and 
Nova  Scotia.  Fig.  266  represents  a  tooth,  half  the  natural 
size,  of  a  Nova  Scotia  species  (Bathygnathus  borealis  of  Leidy); 
and  Fig.  267,  a  tooth  of  another,  from  North  Carolina,  Belodon 
prisons.  Several  kinds  occur  at  Phoenixville,  Pa.,  where  there 
is  literally  a  bone-bed. 

Figs.  268  -  270  a,  represent  the  tracks  of  three  species  of 
Eeptiles  from  the  Connecticut  Valley  beds ;  268  -  270  are  the 

Figs.  266-270. 


REPTILES.  —  Fig.  266,  Bathygnathus  borealis  (x  J);  267,  Belodon  priscus  ;  267  a,  section 
of  same ;  268,  268  a,  fore  and  hind  feet  of  Anisopus  Deweyanus  (x  £) ;  269,  269  a,  ibid,  of 
A.  gracilis  (x  §);  270,  270  a,  ibid,  of  Otozoum  Moodii  (x  iV). 

impressions  made  by  the  fore-foot  in  each,  and  268  a,  269  a, 
270  a,  of  the  hind  foot.  Fig.  270  is  reduced  to  one  eighteenth 
the  natural  size,  the  actual  length  of  the  track  being  20  inches. 
The  animal  is  called  Otozoum  Moodii  by  Hitchcock ;  it  appears 
to  have  walked  like  a  biped,  bringing  its  fore-feet  to  the 
ground  only  occasionally,  impressions  of  these  feet  being  sel- 
dom found.  The  animal  had  a  stride  of  3  feet,  and  must  have 
been  of  formidable  dimensions.  Twenty-one  consecutive 
tracks  of  an  Otozoum  were  exposed  to  view  in  the  summer  of 
1874  in  one  of  the  Portland  quarries. 


TRIASSIC  AND  JURASSIC   PERIODS. 


167 


Some  of  the  Eeptiles  made  three-toed  tracks,  closely  like 
those  of  birds  ;  and  this  fact  has  suggested  the  doubt  whether 
also  the  three-toed  tracks  in  connection  with  which  no  tracks 
of  fore-feet  have  been  found  may  not  be  Keptilian.  These 
Eeptiles  with  three-toed  tracks  have  several  bird-like  char- 
acters ;  they  are  called  Dinosaurs,  this  name,  from  8ewos, 
terrible,  and  cavpos,  lizard,  having  been  given  to  some  gigan- 
tic species  of  the  Jurassic  and  Cretaceous  periods. 

The  tracks,  which  have  been  regarded  as  those  of  birds  (no 
tracks  of  the  anterior  feet  being  known),  are  very  numerous. 
The  largest  of  them  is  one  and  a  half  feet  long  (Fig.  271),  far  ex- 
ceeding that  of  an  Ostrich,  and  even  surpassing  that  which  the 
giant  Moa  of  New  Zealand  might  have  made  (p.  242).  Fig. 


Figs.  271,  272. 


271 


272 


Fig.  271,  Track  of  Brontozoum  giganteum  (x  £);  272,  Slab  of  sandstone  with  tracks  of 
Birds? and  Reptiles  (x  ^TJ). 

272  represents,  on  a  small  scale,  a  slab  from  the  Connecticut 
Eiver  sandstone  covered  with  tracks  of  reptiles  and  the  sup- 
posed birds,  as  figured  by  Hitchcock.  The  two  tracks  lettered 
a  are  added,  of  larger  proportional  size  than  the  others,  to 
show  more  distinctly  the  form. 


168 


MESOZOIC   TIME.— KEPTILIAN  AGE. 


Pig.  273. 


Jaw-bone  of  Dromatherium  sylvestre. 


The  only  relics  of  Mammals  yet  discovered  in  the  American 
rocks  are  two  jaw-bones  (Fig.  273).  They  are  from  North 
Carolina,  and  belong  to  a  species  of  the  division  of  Mammals 
called  Marsupials  (see  page  50),  the  same  to  which  the 
Opossum  belongs,  which  now  inhabits  the  same  region. 

The  facts  prove  that  the 
land  population  of  Mesozoic 
America  included  Insects, 
Reptiles,  Marsupial  Mammals, 
and  probably  Birds ;  and 
that  the  forests  that  covered 
the  hills  were  mainly  composed  of  Conifers  and  Cycads.  The 
existence  of  birds  is  probable  because  (1)  the  tracks  are  pre- 
cisely those  of  birds  as  well  as  of  Dinosaurs ;  (2)  it  is  im- 
probable that  Mammals,  the  highest  of  Vertebrates,  should 
have  preceded  birds  in  geological  history ;  and  (3)  remains  of 
a  true  bird  have  been  found  in  the  Jurassic  rocks  of  Europe. 

b.  Foreign. 

The  European  and  British  rocks  of  these  periods,  especially 

275  Figs.  274-277. 


RADIATES  :  Fig.  274,  Prionastrsea  oblonga  (a  Coral) ;  275,  Encrinus  liliiformis  (a  Crinoid) ; 
276,  Cidaris  Blumenbachii  (an  Echinus) ;  277,  Spine  of  same. 


TRIASSIC  AND  JURASSIC  PERIODS. 


1G9 


of  the  Jurassic,  abound  in  marine  fossils,  and  afford  a  good 
idea  of  the  Mesozoic  life  of  the  ocean.  The  remains  of  ter- 
restrial life  are  also  of  great  interest,  Marsupial  Mammals 
occurring  in  the  Triassic  beds,  and  birds  in  the  Jurassic. 

1.  Radiates.  —  Polyp-corals  are  common  in  some  Jurassic 
strata :  they  are  related  to*  the  modern  tribe  of  corals,  and  not 
to  the  ancient.     Fig.  274  represents  one  of  the  oolytic  spe- 
cies.    Crinoids  are  of  many  kinds,  yet  their  number,  as  com- 
pared with  other  fossils,  is  far  less  than  in  the  preceding 
ages;   and  they  are  accompanied  by  various  new  forms  of 
Star-fishes  and  Echini  (page  57).     Fig.  275  represents  one 
of  the  Triassic  Crinoids,  the  Lily-Encrinite,  or  Encrinus  lilii- 
formis;  Fig.  276,  an  Echinus,  from  the  Qolyte,  stripped  of  its 
spines ;  and  Fig.  277,  one  of  the  spines  separate. 

2.  Mollusks.  —  Brachiopods  are  few  compared  with  their 
number  in  the  Paleozoic.     The  last  species  of  the  Paleozoic 
genera,  Spirifer  and  Leptcena,  lived  in  the  early  part  of  the 


Figs.  278-281. 
281 


278 


MOLLTJSKS  :  Fig.  278,  Spirifer  "Walcotti ;  279,  Gryphsea  incurva  5  280,  Trigonia  clavellata 
281,  Viviparus  (Paludina)  fluviorum. 

Jurassic  period.  Fig.  278  represents  one  of  these  last  of  the 
Spirifer  group.  Lamellibranchs  and  G-asteropods  abound  in  spe- 
cies, and  under  various  new,  and  many  of  them  modern,  genera. 


170 


MESOZOIC  TIME.  —  REPTILIAN  AGE. 


Species  of  the  genus  Gryphcea  were  common  in  the  Lias  and 
later  Mesozoic  rocks  :  they  are  related  to  the  Oyster,  but  have 
the  beak  incurved.  Fig.  279  represents  a  Liassic  species. 
Trigonia  (Fig.  280)  is  a  characteristic  genus  of  the  Mesozoic ; 
the  name  alludes  to  the  triangular  form  of  the  shell :  the 
species  figured  is  from  the  Ob'lyte.  Fig.  281  represents  a 
fresh-water  snail-shell,  a  very  abundant  fossil  in  the  fresh- 
water limestone  of  the  Wealden,  closely  resembling  many 
modern  species. 

But  the  most  remarkable  and  characteristic  of  all  Mesozoic 
Mollusks  were  the  Ceplialopods.  This  order  passed  its  maxi- 
mum as  to  number  and  size  in  the  Mesozoic,  and  hundreds  of 
species  existed.  The  last  of  the  Paleozoic  types  of  Orthocerata 


Pigs.  282,  283. 


282 


MOLLTJSKS  :  Fig.  282,  Ammonites  Humphreysianus  ;  283,  A.  Jason. 

and  Goniatites  lived  in  the  Triassic  period.  In  the  same  pe- 
riod species  of  Ammonites,  one  of  the  most  characteristic  of 
Mesozoic  groups,  became  common ;  and,  in  the  earliest  Juras- 
sic, the  first  of  Belemnites,  another  peculiarly  Mesozoic  type, 
appeared. 

The  Ammonites  had  external  chambered  shells  like  the  Nau- 


TRIASSIC  AND  JURASSIC  PERIODS.  171 

tili  (page  55)  and  G-oniatites.     Two  Ob'lytic  species  are  repre- 
sented "in  Figs.  282,  283.     One  of  them  (Fig.  283)  has  the 
side  of  the  aperture  very  much  prolonged ;  but  the  outer  mar- 
gin of  the  shell,  whether  prolonged  or  not,  is  seldom  well 
preserved.     The  partitions  (or  septa)  within 
the  shells  of  Ammonites  are  bent  back  in          Flg*  284t 
many  folds  (and  much  plaited  within  each 
fold)  at  their  junction  with  the  shell,  so  as 
to  make  deep  plaited   pockets.     The  front 
view  of  the  outer  plate,  with  the  entrances  to 
its  side-pockets,  are  seen  in  Fig.  284.     The 
fleshy  mantle  of  the  animal  descended  into 
these  pockets,  and  thus  the  animal  was  aided 
in  holding  firmly  to  its  shell.     The  siphuncle 
in  the  Ammonites  is  dorsal.     The  Paleozoic 
Goniatites  were  of  the  Ammonite  family,  but     Ammonites  tornatus. 
the  pockets  were  much  more  simple,  the  flex- 
ures of  the  margins  of  the  partitions  being  without  plications. 

The  fossil  Belemnite  is  the  internal  bone  of  a  kind  of  Ce- 
phalopod,  analogous  to  the  pen  or  internal  bone  (or  osselet)  of 
a  Sepia,  or  Cuttle-fish  (see  Fig.  289).  It  is  a  thick,  heavy  fos- 
sil, of  the  forms  in  Figs.  285,  286,  having  a  conical  cavity 
at  the  upper  end.  The  fossils  are  more  or  less  broken  at  this 
extremity ;  when  entire,  the  margin  of  the  aperture  is  elon- 
gated into  a  thin  edge,  and  sometimes,  on  one  side,  into  a  thin 
plate  of  the  form  in  Fig.  287.  The  animal  had  an  ink-bag 
like  the  modern  Sepia ;  and  ink  from  these  ancient  Cephalo- 
pods  has  been  used  in  sketching  their  fossil  remains.  Fig. 
288  represents  one  of  the  ink-bags  of  the  Jurassic  Cephalo- 
pods.  Fig.  289  is  another  related  Cephalopod,  showing  some- 
thing of  the  form  of  the  animal,  and  also  the  ink-bag  in  place. 

3.  Articulates.  —  The  Articulates  included  various  shrimps, 
or  craw-fishes  (Fig.  290,  a  Triassic  species),  Crabs,  and  Te- 
tradecapod  (or  14-footed)  Crustaceans  (Fig.  291,  representing 
a  species  something  like  the  modern  Sow-bug),  but  no  Tri- 
lobites ;  also  Spiders  (Fig.  292),  and  species  of  many  of  the 


172 


MESOZOIC   TIME.  — REPTILIAN  AGE. 


orders  of  Insects.  Fig.  293  is  a  Libellula,  or  Dragon-fly,  of 
the  Jurassic  period,  from  Solenhofen ;  and  Fig.  294,  the  wing- 
case  of  a  beetle,  from  the  Stonesfield  Oolyte. 


Figs.  285-289. 


MOLLTJSKS  :  Fig.  285,  Belemnites  clavatus ;  286,  B.  paxillosus  ;  286  a,  Outline  of  section 
of  same,  near  extremity ;  287,  View,  reduced,  of  the  complete  osselet  of  a  Belemnite  ;  288, 
Fossil  Ink-bags  of  a  Cephalopod  ;  289,  Acanthoteuthis  antiquus. 

4.  Vertebrates.  —  The  Fishes  were  chiefly  Ganoids  or  Sela- 
chians. In  the  Triassic  beds  of  Europe,  as  in  America,  oc- 
curred the  last  species  of  the  vertebrated-tailed  Ganoids,  and 
the  first  of  those  having  the  tail  not  vertebrated.  Fig.  295 
represents  one  of  the  latter  kind  from  the  Lias.  Among  the 


TRIASSIC  AND  JURASSIC  PERIODS. 


173 


SJiarks  (or  Selachians)  the  Cestraciont  tribe,  one  of  the  most 
ancient,  characterized  by  a  pavement  of  grinding  teeth  (page 

Figs.  290-294. 


ARTICULATES :  Fig.  290,  Pemphix  Sueurii ;  291,  Archseoniscus  Brodiei ;  292,  Palpipes 
priscus ;  293,  Libellula  ;  294,  Wing-case  of  a  Buprestis. 

52),  still  continued,  and  was  very  numerously  represented. 
There  were  also,  in  the  Jurassic  beds,  Sharks  having  sharp- 


rig.  295. 


295  a 


VERTEBRATE :  Fig.  295,  Restored  figure  of  .Echmodus  (Tetragonolepis)  from  the  Lias 
( x  4) ;  295  a,  Scales  of  same. 

edged  teeth  like  those  of  the  tribe  of  Sharks  that  inhabits 
modern  waters. 

Reptiles  were  the  dominant  race  in  the  Eeptilian  world. 


174 


MESOZOIC  TIME.  — REPTILIAN  AGE. 


Among  them  Amphibians,  the  division  most  common  in  the 
Carboniferous  age,  passed  their  climax  in  the  Triassic,  while 
true  Keptiles  expanded  and  reached  their  maximum  of  size 
and  grade  near  the  close  of  the  Jurassic  or  in  the  earlier  half 
of  the  Cretaceous  period. 


Figs.  296-298. 


VERTEBRATES  :  Fig.  296,  Skull  of  Mastodonsaurus  giganteus  (x 
(x  £);  298,  Footprints  of  Cheriotherium  (x 


j  297,  Tooth  of  same 


The  latter  included  species  for  each  of  the  elements,  —  the 
water,  the  earth,  and  the  air. 

Among  the  Triassic  Amphibians,  one  frog-like  Ldbyrintho- 
dont  had  a  skull  over  2  feet  long,  of  the  form  shown  in  Fig. 
296  ;  its  mouth  was  set  round  with  teeth  3  inches  long  (Fig. 
297),  and  the  body  was  covered  with  scales.  The  specimen 
here  figured  was  found  in  Saxony.  It  is  probable  that  some 
of  the  American  Reptilian  species  whose  tracks  are  so  com- 
mon in  the  Connecticut  Valley  were  of  this  type.  Fig.  298  is 
a  reduced  view  of  hand-like  tracks,  from  the  same  locality  as 
the  above,  supposed  to  have  been  made  by  an  animal  of  the 
same  species.  The  frogs  of  the  present  day  are  feeble  and 
diminutive  compared  with  the  Triassic  Amphibians. 

Among  true  Reptiles  there  were,  first,  Swimming  Beptiles, 
—  called  Enaliosaurs  because  of  their  living  in  the  sea  (from 
the  Greek  evd\iost  of  the  sea,  and  cravpos,  lizard)  ;  they  prob- 


TRIASSIC  AND   JUEASSIC   PERIODS. 


175 


ably  existed  in  the  Carboniferous  age  (page  132),  but  became 
numerous  and  of  great  size  in  the  Middle  Mesozoic.  They 
had  paddles  like  Whales,  and  thus  were  well  fitted  for  marine 
life.  The  most  common  kinds  were  the  Ichthyosaurs  and  Ple- 
siosaurs. 

Figs.  299-303. 


VERTEBRATES:  Fig.  299,  Ichthyosaurus  com  munis  (x  TOTT)  :  300,  Head  of  same  (  x 
301  a,  301  b,  View  and  section  of  vertebra  of  same  ( x  £) ;  302,  Tooth  of  same,  natural 
size  ;  303,  Plesiosaurus  dolichodeirus  (  x  inj) ;  303  a,  303  6,  View  and  section  of  vertebra 
of  same. 

The  Ichthyosaurs  (Fig.  299)  had  a  short  neck,  a  long  and 
large  head,  enormous  eyes,  and  thin,  doubly-concave,  and 
therefore  fish-like,  vertebrae.  The  name  is  from  the  Greek 
Iffirt*  fish,  and  <ravpos,  lizard.  Fig.  300  represents  the  head 
of  an  Ichthyosaur,  one  thirtieth  the  natural  length,  showing 
the  large  size  of  the  eye  and  the  great  number  of  the  teeth. 
Fig.  301  I  is  one  of  the  vertebrae,  reduced,  and  Fig.  301  a,  a 
transverse  section  of  the  same,  exhibiting  the  fact  that  both 
surfaces  are  deeply  concave,  nearly  as  in  fishes  ;  Fig.  302  is 
one  of  the  teeth,  natural  size.  Some  of  the  Ichthyosaurs  were 
30  feet  long. 


176  MESOZOIC   TIME.  —  REPTILIAN   AGE. 


The  Plesiosaurs  (named  from  the  Greek  TrX^er/o?,  near,  and 
<ravpo<:t  because  not  quite  like  a  Saurian),  one  of  which  is  rep- 
sented  very  much  reduced  in  Fig.  303,  had  a  long  snake-like 
neck,  a  comparatively  short  body,  and  a  small  head.  Fig. 
303  a  represents  one  of  the  vertebrae,  and  303  b,  a  section 
of  the  same  ;  it  is  doubly  concave,  but  less  so,  and  much 
thicker,  than  in  the  Ichthyosaurs.  Some  species  of  Plesiosaur 
were  25  to  30  feet  long.  Another  related  Reptile,  called  a 
Pliosaur,  was  30  to  40  feet  long.  Remains  of  more  than  50 
species  of  Enaliosaurs  have  been  found  in  the  Jurassic  rocks. 

Besides  these  swimming  Saurians,  there  were  numerous 
species  of  Lacertians  (Lizards)  and  Crocodilian*  10  to  50  feet 
long,  and  Dinosaurs,  the  bulkiest  and  highest  in  rank  of  the 
Saurians,  25  to  60  feet  long. 

To  the  group  of  Dinosaurs  belongs  the  Iguanodon,  of  the 
Wealden  beds,  first  made  known  by  Dr.  Mantell,  whose  body 
was  28  to  30  feet  long,  and  which  stood  high  above  the 
ground  quadruped-like,  the  femur,  or  thigh-bone,  alone  being 
nearly  3  feet  long.  The  hind  feet  were  three-toed  like  those 
of  birds.  Its  habits  are  supposed  to  have  been  like  those  of 
the  ancient  sloth-like  animal  called  a  Megatherium  (page  235), 
—  the  animal  grazing  on  the  trees  along  the  borders  of  the 
marshes,  estuaries,  or  streams  in  or  about  which  it  lived,  and 
able  to  lift  its  body  on  its  hind  legs  for  this  purpose.  It  had 
teeth  like  the  modern  Iguana,  (and  hence  the  name,  from 
Iguana,  and  the  Greek  080^9,  tooth),  but  it  had  proportionately 
a  much  shorter  tail.  The  Megalosaur  was  another  of  the 
gigantic  Dinosaurs  of  the  later  part  of  the  Jurassic  period  ; 
it  was  a  terrestrial  carnivorous  Saurian  about  30  feet  in  length, 
and  was  better  fitted  in  its  limbs  for  raising  its  body  toward 
an  erect  posture.  The  three-toed  American  Reptiles,  whose 
tracks  are  described  on  page  167,  are  those  of  other  Dinosaurs  ; 
and  these  had  the  habit  of  bipeds.  Many  points  in  the 
structure  of  the  limbs  and  pelvis  of  the  Dinosaurs  are  similar 
to  those  of  birds. 

The  Reptiles  adapted  for  the  air  —  that  is,  for  flying  —  are 


TRIASSIC  AND  JURASSIC  PERIODS.  177 

designated   Pterosaurs,  from   the   Greek   Trrepov,    wing,  and 

o-avpos.     The  most  common  genus    is    called  Pterodactylus. 

The  general  form  of  a  Pterodactyl  is  shown  in  Fig.  304.     The 

•  bones  of  one  of  the  fingers  are  greatly  elongated,  for  the  purpose 

Fig.  304. 


VERTEBRATE.  —  Pterodactylus  crassirostris  (  x 


of  supporting  an  expanded  membrane,  so  as  to  make  it  serve 
(like  an  analogous  arrangement  in  bats)  for  flying.  The  name 
Pterodactyl  is  from  the  Greek  TrrepoV,  wing,  and  8a«Tu\o9, 
finger.  The  Jurassic  Pterodactyls  were  mostly  small,  and 
probably  had  the  habits  of  bats  ;  the  largest  had  a  spread  of 
wing  of  about  10  feet,  Unlike  our  common  birds,  they  had 
a  mouth  full  of  teeth,  and  no  feathers.  As  Bats  are  flying 
Mammals,  so  the  Pterosaurs  are  simply  flying  Eeptiles,  and 
have  little  resemblance  to  birds  in  structure,  except  that 
their  bones  are  hollow,  and  adapted  in  form  for  the  bird- 
like  characteristic  of  flying. 

Besides  the  kinds  of  Reptiles  already  mentioned,  there  were 
Turtles  in  the  Jurassic  period;  but,  according  to  present 
knowledge,  the  world  contained  no  true  Snakes. 

Coprolites  (or  fossil  excrements)  of  both  Reptiles  and  Fishes 
are  common  in  the  bgne-beds.  When  cut  and  polished  they 

8*  L 


178  MESOZOIC  TIME.  —  REPTILIAN  AGE. 

Fig.  305. 


VERTEBRATE.  —  Archseopteryx  macrura. 


TRIASSIC   AND   JURASSIC   PERIODS. 


179 


have  a  degree  of  beauty  sufficient  to  give  them  some  value  in 
jewelry. 

Eemains  of  Birds  have  been  found  in  the  quarries  of  Solen- 
hofen  (page  166).  They  have  revealed  the  fact  that  some  at 
least  of  the  Mesozoic  Birds  (and  of  America,  beyond  question, 
as  well  as  Europe)  were  reptilian  in  some  of  their  characters. 
The  skeleton  found  (Fig.  305)  shows  that  the  Birds  had  long 
reptile-like  tails  consisting  of  many  vertebrae,  and  finger-like 
claws  on  the  fore  limb  or  wing,  like  those  of  the  Pterodactyl 
and  Bat,  fitting  them  evidently  for  clinging.  But,  while 
thus  reptilian  in  some  points  of  structure,  they  were  actually 
Birds,  being  feathered  animals,  and  having  the  expanse  of 
the  wing  made,  not  by  an  expanded  membrane  as  in  the 
Pterodactyl,  but  by  long  quill-feathers.  The  tail-quills  were 

Figs.  306,  307. 


VERTEBRATES.  —  Fig.  306,   Amphitherium   Broderipii    (x2);    307,   Phascolotherium 
Bucklandi  (x  2). 

arranged  in  a  row  either  side  of  the  long  tail.     The  feet  were 
like  those  of  birds. 

Eemains  of  Mammals  occur  in  the  Upper  Trias  (or  base 
of  the  Lias)  of  Germany,  in  the  Lower  Oolyte  deposit  at 
Stonesfield,  England,  and  in  the  Middle  Purbeck  beds  of  the 
Upper  Oolyte  (page  161).  Nearly  20  species  have  been  made 
out,  14  of  them  from  relics  in  the  Middle  Purbeck.  The 
larger  part,  if  not  all,  are  Marsupials.  Figs.  306,  307  repre- 
sent the  jaws  of  two  species  from  Stonesfield,  magnified  twice 
the  natural  size. 


180  MESOZOIC   TIME.  — REPTILIAN   AGE. 

As  Marsupials  are  semi-oviparous  Mammals,  and  therefore 
are  intermediate  between  ordinary  Mammals  and  the  inferior 
and  oviparous  Vertebrates  (page  50),  it  follows  that  both  the 
Birds  and  Mammals  of  the  Mesozoic  were  in  part,  at  least, 
comprehensive  or  intermediate  types,  and  partook  of  reptilian 
features  in  the  Eeptilian  age. 

3.    General  Observations. 

1.  American  Geography.  —  The  Triassico- Jurassic  sand- 
stones and  shales  of  the  Atlantic  border  region  are  sedimen- 
tary beds ;  consequently,  the  long  narrow  ranges  of  country 
in  which  they  were  formed  were  occupied  at  the  time  more  or 
less  completely  by  water. 

The  absence  of  true  marine  fossils  has  been  remarked  upon 
as  proving  that  this  water  was  either  brackish  or  fresh ;  and 
hence  the  areas  were  estuaries  or  deep  bays  running  far  into 
the  land. 

There  was  probably  an  abundance  of  marine  life  in  the 
ocean,  if  we  may  judge  from  its  diversity  on  the  other  side 
of  the  Atlantic ;  but  the  sea-coast  of  the  era  must  have  been 
outside  of  the  present  one,  so  that  any  true  marine  or  sea-coast 
deposits  that  were  made  are  now  submerged.  The  present 
sea-border  is  shallow  for  a  distance  of  80  miles  from  the  New 
Jersey  coast,  the  depth  of  water  at  this  distance  out  being 
but  600  feet. 

As  all  the  depressions  or  valleys  occupied  by  the  estuaries 
are  parallel  with  the  Appalachians  (page  164),  and  since  the  era 
of  the  formations  was  that  next  following  the  origin  of  these 
mountains,  the  depressions  were  probably  made  at  the  time 
the  Appalachian  foldings  were  in  progress,  or  are  great  valleys 
or  depressions  then  left  in  the  surface. 

The  level  of  the  several  sandstone  areas  above  the  ocean 
proves  that  the  land  at  the  time  was  not  far  from  its  present 
elevation,  and  therefore  that  the  Appalachians  had  probably 
nearly  their  present  height. 

The   deposits   contain   footprints,  ripple-marks,  rain-drop 


TRIASSIC  AND  JURASSIC  PERIODS.  181 

impressions,  and  other  evidences,  on  many  of  the  layers,  that 
they  were  formed  partly  in  shallow  waters,  and  partly  as 
sand-flats,  or  emerging  marshes  and  shores,  over  which  reptiles 
and  birds  might  have  walked  or  waded.  If,  then,  they  are 
several  thousands  of  feet  thick,  there  must  have  been  a 
progressing  subsidence  of  the  valley-depressions,  —  that  is,  a 
sinking  must  have  been  going  on.  It  is  hence  apparent  that 
oscillations  of  level,  like  those  that  characterized  the  Appala- 
chian region  before  and  during  the  Appalachian  revolution, 
were  in  progress.  Two  effects  of  this  subsidence  occurred ; 
(1)  The  sandstone  beds  were  more  or  less  faulted  and  tilted, 
those  of  the  Connecticut  Valley  receiving  a  dip  to  the  eastward, 
or  southeastward,  those  of  New  Jersey  and  Pennsylvania  to 
the  northwestward.  (2)  In  the  sinking  of  the  valley-depres- 
sion, an  increasing  strain  was  produced  in  the  earth's  crystal- 
line crust  beneath,  which  finally  became  so  great  that  the  crust 
broke,  fissures  opened,  and  liquid  rock  came  up.  The  dikes 
and  ridges  of  trap  are  this  liquid  rock  solidified  by  cooling. 
The  existence  of  the  dikes,  and  their  parallelism  to  the  general 
course  of  the  valley-depressions,  prove  —  (1)  the  fact  of  the 
fractures ;  (2)  their  resulting  from  the  same  cause  which  pro- 
duced the  sinking ;  and  (3)  the  fact  of  the  igneous  ejections. 
The  earth's  crust  along  the  Connecticut  Valley  was  thus  a 
scene  of  igneous  operations  for  more  than  100  miles,  and 
through  a  vast  number  of  opened  fissures.  All  the  Trias- 
sico-Jurassic  areas  from  Nova  Scotia  to  Southern  North  Caro- 
lina, a  distance  of  1,000  miles,  were  similarly  broken  through 
and  invaded  by  trap  ejections.  The  Palisades  of  the  Hudson 
date  from  this  period,  —  probably  the  middle  or  later  part  of 
the  Jurassic  period. 

The  Western  Interior  or  Rocky  Mountain  region  had  been 
mostly  submerged  during  the  Carboniferous  age,  as  shown  by 
the  fact  that  limestones  were  forming  there  in  the  Coal-Meas- 
ure period,  and  fossiliferous  sandstones  in  the  Permian.  The 
Triassic  sandstone  there  proves,  by  its  nature,  its  gypsum  in 
many  places,  and  the  paucity  of  fossils,  that,  by  some  change, 


182  MESOZOIC   TIME.  —  REPTILIAN  AGE. 

the  region  had  become  mostly  an  interior  shallow  salt  sea, 
shut  off  to  a  great  extent  from  the  ocean.  Such  a  sea  would 
have  been  made  too  fresh  for  marine  life  in  the  rainy  season, 
and  probably  too  salt  for  almost  all  life  in  the  hot  season. 
Hence,  life  would  have  been  nearly  or  quite  absent.  The 
salt  waters  by  evaporation  would  have  furnished  gypsum  to 
the  beds,  as  happens  now  sometimes  from  sea-water.  It  fol- 
lows, then,  from  the  beds  of  the  Atlantic  border  as  well  as 
those  of  the  Western  Interior,  that  the  continent  during  the 
era  of  these  Mesozoic  beds  was  to  a  less  extent  submerged 
than  in  the  greater  part  of  the  Paleozoic  ages  and  the  follow- 
ing portion  of  the  Mesozoic.  The  fossiliferous  Jurassic  beds 
overlying  the  western  Triassic  show  that,  before  the  Jurassic 
period  had  closed,  the  sea  had  again  free  access  over  it  and 
oceanic  life  was  abundant. 

2.  Foreign  Geography.  —  The  nature  of  the  Triassic  beds 
of  Britain  and  Europe  shows  that  there  were  large  shallow  in- 
terior seas  also  on  the  eastern  side  of  the  Atlantic.  The  salt- 
deposits  in  the  beds,  the  paucity  of  fossils  in  the  most  of  the 
strata,  and  the  prevalence  of  marlytes,  indicate  the  same  con- 
ditions as  existed  in  New  York  during  the  formation  of  the 
Saliferous  beds  of  the  Upper  Silurian  (see  page  100),  and 
somewhat  similar  to  those  in  which  the  Kocky  Mountain 
Gypsiferous  formation  originated.  The  limestone  that  inter- 
vened along  the  Rhine,  between  the  two  formations  of  sand- 
stone and  marlytes,  shows  an  interval  of  more  open  sea ;  yet 
the  impurity  of  the  limestone  suggests  that  the  ocean  had  not 
full  sweep  over  the  region. 

The  beds  of  the  Jurassic  period  are  almost  all  of  them 
evidence,  both  from  their  constitution  and  their  abundant 
marine  life,  that  the  free  ocean  again  had  sway  over  large 
portions  of  the  Continental  area.  Its  limits  in  Great  Britain, 
however,  became  more  contracted  as  the  period  passed,  and 
toward  its  close  fresh- water  and  terrestrial  beds  were  forming 
in  some  places  that  had  earlier  in  the  period  been  under  salt 
water. 


TRIASSIC  AND  JURASSIC  PERIODS.  183 

3.  Climate.  —  The  Jurassic  coral-reefs  of  Britain  indicate 
that  England  then  lay  within  the  sub-tropical  oceanic  zone. 
This  zone  now  has  the  parallel  of  27°  to  28°  as,  in  general,  its 
outer  limit  (lying  mostly  between  20°  and  27°) ;  and,  conse- 
quently, its  Jurassic  limit,  if  including  England,  reached  twice 
as  far  toward  the  pole  as  now.  It  is  possible,  however,  that 
the  line  would  have  run  along  the  British  Channel,  were  it 
not  for  the  Gulf  Stream  of  the  era,  which  carried  the  sub- 
tropical temperature  northeastward  through  the  British  seas, 
as  it  now  does  to  Bermuda,  in  latitude  34°. 

The  following  are  other  facts  of  similar  import.  In  Arctic 
America  species  of  shells  allied  to  those  of  Europe  and  tropi- 
cal South  America  occur  in  latitudes  60°  to  77°  16';  and  one 
species  of  Bdemnite  and  one  of  Ammonite  are  said  to  be  iden- 
tical with  species  occurring  in  these  two  remote  and  now 
widely  different  regions.  If  not  absolutely  identical,  the  evi- 
dence from  them  as  to  oceanic  temperature  is  nearly  the 
same.  Moreover,  on  Exmouth  Island,  in  77°  16'  N.,  remains 
of  an  Ichthyosaur  have  been  found,  and  in  76°  22'  1ST.,  on 
Bathurst  Island,  bones  of  other  large  Jurassic  Eeptiles  (Teleo- 
saurs).  It  is  probable,  therefore,  that  a  warm-temperate 
oceanic  zone  covered  the  Arctic  to  the  parallel  of  78°,  if  not 
beyond.  No  large  living  reptiles  exist  outside  of  the  warm- 
temperate  zone. 

DISTURBANCES   CLOSING   THE  JURASSIC   PERIOD. 

After  the  Jurassic  period,  or  near  its  close,  the  lofty  ranges 
of  the  Sierra  Nevada,  on  the  eastern  boundary  of  California 
and  the  western  of  the  Great  Plateau  or  Basin ;  of  the  Wah- 
satch,  on  the  eastern  boundary  of  the  same  plateau,  just  east 
of  Great  Salt  Lake ;  and  of  the  Humboldt  Eanges  over  this 
plateau,  besides  other  ranges,  were  made.  Triassic  and  Ju- 
rassic fossils  have  been  found  in  the  rocks  of  the  Sierra  Ne- 
vada, while  Cretaceous  fossiliferous  beds  lie  unconformably 
over  the  upturned  strata  of  the  mountains;  the  latter  fact 


184  MESOZOIC   TIME.  —  REPTILIAN  AOE. 

proving  that  the  mountain-making  occurred  before  the  Creta- 
ceous era,  and  the  former,  that  it  took  place  after  the  Juras- 
sic era.  The  ejections  of  trap  in  the  Triassico- Jurassic  areas 
of  the  Atlantic  border  occurred  previous  to  the  Cretaceous 
period,  and  perhaps  contemporaneously  with  the  making  of 
the  mountains  on  the  Pacific  border. 


2.  Cretaceous  Period. 

General  characteristics.  —  The  Cretaceous,  while  the  closing 
period  of  Mesozoic  time,  was  also,  in  some  respects,  a  tran- 
sition era  between  the  Mesozoic  and  Cenozoic.  During  its 
progress,  as  is  explained  beyond,  occurred  the  decline,  and,  at 
its  close,  the  extinction,  of  a  large  number  of  the  tribes  of  the 
mediaeval  world,  while,  at  the  same  time,  there  appeared  in 
its  course  other  tribes  eminently  characteristic  of  the  modern 
world.  Among  the  modernizing  features,  the  most  prominent 
are  the  Palms  and  Angiosperms  among  plants,  and  the  Teliosts 
among  fishes. 

The  Palms  and  Angiosperms  include  nearly  all  the  fruit- 
trees  of  the  world,  and  constitute  far  the  larger  part  of  mod- 
ern forests.  The  Conifers  and  Cycads,  wherever  they  now 
occur  near  groves  of  Angiosperms,  exhibit  the  contrast  be- 
tween the  mediaeval  foliage  and  that  of  the  present  age.  The 
Teliosts  (page  50)  embrace  nearly  all  modern  fishes  excepting 
those  of  the  order  of  Sharks,  or  Selachians.  Their  prevalence 
was  as  great  a  change  for  the  waters  as  the  new  tribes  of 
plants  for  the  land. 

I.    Rocks:   Kinds  and  Distribution. 

In  North  America,  the  Cretaceous  formation  borders  the 
continent  on  the  Atlantic  side,  south  of  New  York,  and  along 
the  north  and  west  sides  of  the  Gulf  of  Mexico ;  besides,  it 
spreads  up  the  Mississippi  Valley  to  the  mouth  of  the  Ohio ; 
and,  more  to  the  westward,  from  Texas,  northward,  over  the 
slopes  of  the  Rocky  Mountains,  being  now  at  a  height  in  some 


CRETACEOUS  PERIOD.  185 

places  of  10,000  to  12,000  feet  above  the  sea.  Its  beds  are 
exposed  to  view  in  New  Jersey  and  in  some  portions  of  the 
more  southern  Atlantic  States,  though  mostly  covered  by  the 
Tertiary.  They  are  largely  displayed  through  Alabama  and 
Mississippi,  and  cover  a  great  area  west  of  the  Mississippi. 
(See  map,  page  60.)  In  the  Eocky  Mountain  region  they 
occur  east  of  the  Wahsatch,  and  south  in  Colorado,  New 
Mexico,  and  beyond;  also  west  of  the  Sierra  Nevada  in 
California  of  great  thickness.  In  Colorado  and  New  Mexico, 
and  on  Vancouver's  Island,  there  are  valuable  beds  of  brown 
coal  (sometimes  called  lignite)  in  the  Cretaceous  formation. 
The  coal-beds  of  Wyoming  and  Utah,  near  the  Central 
Pacific  Railroad,  and  part  of  those  to  the  south,  are  made 
Cretaceous  by  some  geologists,  and  by  others,  Tertiary. 

In  England  the  formation  occupies  a  region  just  east  of 
the  Jurassic,  stretching  from  Dorset  on  the  British  Channel 
eastward,  and  also  northeastward  to  Norfolk,  on  the  German 
Ocean,  and  continuing  near  the  borders  of  this  ocean,  still 
farther  north,  beyond  Flamborough  Head :  it  is  numbered  9 
on  the  map,  page  118.  Cretaceous  rocks  occur  also  in  North- 
ern and  Southern  France,  and  many  other  parts  of  Europe, 
covering  much  of  the  territory  between  Ireland  and  the 
Crimea,  1,140  miles  in  breadth,  and,  between  the  south  of 
Sweden  and  south  of  Bordeaux,  840  miles. 

-Among  the  rocks  there  are  the  following  kinds:  the  soft 
variety  of  limestone  called  chalk ;  hard  limestones ;  ordinary 
hard  sandstones ;  shales  and  conglomerates  like  those  of  other 
ages  ;  but,  more  common  than  these,  soft  sand-beds,  clay-beds, 
and  shell-beds,  so  imperfectly  consolidated  that  they  may  be 
turned  up  with  a  pick. '  '* 

Many  of  the  sand-beds  or  sandstones  have  a  dark  green 
color,  and  are  called  green-sand.  The  green  color  is  owing  to 
the  presence  of  dark  green  grains  which  occur  mixed  with 
more  or  less  of  common  sand. »  They  are  a  hydrous  silicate  of 
iron  and  potash.  This  green-sand  is  often  used  for  fertilizing 
land,  and  when  so  used  it  is  called  marl ;  it  is  extensively 
quarried  for  this  purpose  in  New  Jersey. 


186  MESOZOIC  TIME.  — REPTILIAN  AGE. 

Chalk-beds  are  the  source  of  flint.  The  flint  is  distributed 
through  the  chalk  in  layers,  these  layers  being  made  up  of 
nodules  of  flint,  or  masses  of  irregular  forms.  Although  often 
of  rounded  forms,  they  are  not  water- worn  stones  of  foreign 
origin,  but  were  formed  in  place,  like  the  hornstone  in  the 
Corniferous  limestone  of  New  York  (page  103). 

Chalk  constitutes  a  large  proportion  of  the  Cretaceous  for- 
mation in  England  and  some  parts  of  Europe.  It  occurs  in  the 
Cretaceous  of  Western  Kansas,  but  not  on  the  Atlantic  border. 

The  succession  of  beds  in  England  is  as  follows :  1.  The 
Lower  Cretaceous,  consisting  largely  of  the  Green-sand  and 
other  arenaceous  beds,  called  collectively  the  Lower  Green- 
sand;  2.  The  Middle  Cretaceous,  containing  the  Upper  Green- 
sand  and  some  other  beds ;  3.  The  Upper  Cretaceous,  compris- 
ing the  Chalk-beds,  the  lower  part  of  which  is  without  flints. 

The  Cretaceous  beds  in  North  America  consist  of  layers  of 
Green-sand,  thick  sand-beds  of  other  kinds,  clays,  shell-beds, 
and,  in  some  places  in  the  States  bordering  on  the  Mexican 
Gulf  (especially  in  Texas),  limestone.  The  thickness  of  the 
formation  in  New  Jersey  is  400  to  500  feet;  in  Alabama, 
2,000  feet ;  in  Texas  about  800,  nearly  all  of  it  compact  lime- 
stone ;  in  the  region  of  the  Upper  Missouri,  2,000  to  2,500 
feet ;  east  of  the  Wahsatch,  9,000  feet  or  more. 

2.    Life. 
1.  Plants. 

The  first  of  Angiosperms  and  of  Palms,  as  already  stated, 
date  from  the  Cretaceous  period.  Leaves  of  a  few  American 
species  of  the  former  are  represented  in  Figs.  308-311 ;  Fig. 
309,  of  a  species  of  Sassafras ;  Fig.  310,  a  Liriodendron ;  and 
Fig.  311,  a  Willow  ;  and  with  these  occur  leaves  of  Oak,  Dog- 
wood, Seech,  Poplar,  etc. 

Besides  these  highest  of  plants,  there  were  also  Conifers, 
Ferns,  and  Sea- weeds,  as  in  former  time,  with  some  Cycads. 
The  microscopic  Algae  called  Diatoms  (page  61),  which  make 


CRETACEOUS  PERIOD. 


187 


siliceous  shells,  and  others  called  Desmids  (page  61),  which 
consist  of  one  or  a  few  simple  green  cellules,  were  very  abun- 
dant. Both  occur  fossil  in  flint ;  and  a  species  of  the  latter 


Figs.  308-311. 


309 


Pig.  308,  Leguminosites  Marcouanus  ;  309,  Sassafras  Cretaceum  ;  310,  Liriodendron  Meekii ; 
811,  Salix  Meekii. 

is  very  similar  to  one  from  the  Devonian  hornstone  figured 
on  page  108  (Fig.  180).  The  Diatoms  are  believed  to  have 
contributed  part  of  the  silica  of  which  the  flint  is  formed. 

2.    Animals. 

1.  Protozoans.  —  The  simplest  of  animals,  Rhizopods,  of  the 
group  of  Protozoans  (page  59),  were  of  great  geological  im- 
portance in  the  Cretaceous  period ;  for  the  Chalk  is  supposed 
to  be  made  mostly  of  their  minute  calcareous  shells.  The 
powdered  chalk  is  often  found  to  contain  large  numbers  of 
these  shells,  the  great  majority  of  which  do  not  exceed  a 


188  MESOZOIC  TIME.  — REPTILIAN  AGE. 

Fig.  312. 


Euplectella  speciosa,  or  Glass  Sponge. 


CRETACEOUS   PERIOD. 


189 


pin's  head  in  size.  A  few  of  the  forms  are  represented  in 
Figs.  313  to  317,  all  very  much  enlarged,  except  317,  which 
is  natural  size.  A  very  common  kind  resembles  Fig.  99,  page 


313 


Pigs.  313-317. 
315  316 


Fig.  318. 


RHIZOPODS :  Fig.  313,  Lituola  nautiloidea ;  314,  Flabellina  rugosa ;  315,  Chrysalidina 
gradata  ;  316,  Cuneolina  pavonia ;  317,  Orlntolina  Texana. 

59,  and  is  called  a  Eotalia.     Fig.  317  represents  a  large  disk- 
shaped  species,  called  an  Orbitolina,  from  Texas. 

Besides  the  above  Protozoans,  Sponges  were  also  very 
abundant,  and  their  siliceous  spicules  (page  59)  were  another 
important  source  of  the  silica  of  the 
flints.  Some  of  the  Sponges,  both 
of  the  Cretaceous  era  and  of  mod- 
ern time  in  the  deeper  seas,  consist 
wholly,  or  nearly  so,  of  silica.  One 
of  the  modern  species,  from  deep 
water  in  the  Indian  Ocean,  is  rep- 
resented in  Fig.  312.  It  consists  of 
a  delicate  network  of  fibres  of  silica, 
and  looks  as  if  made  of  spun  glass. 
The  Ventriculites  were  large  Creta- 
ceous sponges  of  similar  character,  having  an  inverted  conical 
shape.  Fig.  318  represents  another  kind  which  was  prob- 
ably siliceous. 

2.  Radiates.  —  Mollusks.  —  Corals  and  Echini  were  common 
among  Eadiates.  Mollusks  abounded,  both  of  the  Ammonite 
and  Belemnite  types,  besides  others  of  genera  not  peculiar  to 
the  Mesozoic.  Many  of  the  genera  are  represented  in  mod- 
ern seas. 


SPONGE.  —  Siphonia  lobata. 


190 


MESOZOIC   TIME.  —  REPTILIAN  AGE. 


Figs.  319  -  322  are  of  some  of  the  most  characteristic  La- 
mellibranchs  from  the  American  Cretaceous;  Fig.  31.9,  an 
Exogyra  ;  Fig.  320,  an  Inoceramus  ;  Figs.  321,  322,  species  of 
Gryphcea, —  genera  now  extinct.  Figs.  323,  324  represent 
shells  of  Gasteropods,  and  325  to  329,  Cephalopods,  —  all 
American  except  327 ;  Fig.  325,  an  upper  front  view  of  an 
Ammonite,  showing  the  pockets  along  the  sides  of  one  of  the 
partitions  ;  Fig.  325  a,  a  reduced  view  of  the  same  Ammonite 
in  profile ;  Figs.  326  to  328,  three  species  of  the  Ammonite 
family,  but  not  true  Ammonites,  —  one,  Fig.  326,  being  called 
a  ScaphMes  (from  the  Latin  scapha,  a  skiff),  resembling  an 

Figs.  319-322. 


319 


321 


MOLLTJSKS :  Fig.  319,  Exogyra  arietina ;  320,  Inoceramus  problematicus ;  321,  Gryphsea 
vesicularis ;  322,  G.  PitcherL 

Ammonite  with  the  shell  partly  uncoiled,  and  thus  made 
somewhat  to  resemble  a  boat;  Fig.  327,  a  Turrilites,  or  tur- 
reted  Ammonite,  an  anomaly  in  the  family,  as  the  species  are 
almost  all  coiled  in  a  plane ;  Fig.  328,  a  Baculites,  or  straight 
Ammonite,  so  named  from  the  Latin  baculum,  a  walking-stick. 
Some  of  the  Ammonites  of  the  Cretaceous  period  are  3  to  4 
feet  in  diameter. 

Fig.  329  represents  a  common  New  Jersey  Belemnite. 


CRETACEOUS  PERIOD. 


191 


3.  Vertebrates.  —  Among  Vertebrates  there  were  great  num- 
bers of  the   Teliost  or  Osseous  Fishes,  —  fishes  allied  to  the 


Figs.  323-329. 


326  a 


MOLLUSKS  :  Fig.  323,  Fasciolaria  buccinoides ;  324,  Pyrifusus  Newberryi ;  325,  Ammo- 
nites placenta  ;  325  a,  id.,  in  profile,  reduced  ;  326,  Scaphites  larvsrformis  ;  327,  Turrilites 
catenatus ;  328,  Baculites  ovatus  ;  329,  Belemnitella  mucronata. 


perch,  salmon,  pickerel,  etc.     They  occur  along  with  numer- 


192 


MESOZOIC   TIME.  —  REPTILIAN  AOE. 


ous  Sharks  of  both  ancient  and  modern  types  (Cestracionts 
and  Squalodonts),  and  many  also  of  Ganoids.  Thus  the  an- 
cient and  modern  forms  of  fishes  were  united  in  the  popu- 
lation of  the  Cretaceous  seas,  the  former,  however,  making 


Fig.  330. 


Osmeroides  Lewesiensis  (x 


hardly  more  than  a  tenth  of  the  species.     Fig.  330  represents 
one  of  these  Teliost  Fishes,  related  to  the  Salmon  and  Smelt, 


Figs.  331,  332. 


MOSASATTRS  :  Fig.  331,  Mosasaurus  Hoffmanni  (  x 

dispar  (xj). 


j  332,  Side  of  jaw  of  Edestosaurus 


CRETACEOUS  PERIOD. 


193 


Pig.  333. 


from  the  Chalk  at  Lewes,  England.     There  were  also  Herring, 
and  many  other  kinds. 

The  Eeptiles  included  species  of  several  of  the  Jurassic 
genera.  Of  these,  there  were  PTEROSAURS,  of  the  genus  Ptero- 
dactylus,  and  others,  some,  from  Kansas  rocks,  20  to  25  feet 
in  expanse  of  wing  ;  ENALIOSAURS,  or  Sea-Saurians,  of  the 
genera  Ichthyosaurus,  Plesiosaurus,  etc.,  10  to  50  feet  long; 
and  DINOSAURS,  of  the  genera  Iguanodon,  Hadrosaurus,  Lcelaps 
(related  to  the  Megalosaurs),  etc.,  some  of  them  fitted  to  raise 
themselves  and  walk  on  their  hind  feet,  like  the  three-toed 
Eeptiles  of  the  Triassico-Jurassic  era,  in  the  Connecticut 
Valley  (p.  167). 

There  was  also  a  tribe,  unknown  before  the  Cretaceous,  that 
of  the  MOSASAURS  :  great  snake-like  Eeptiles,  15  to  75  feet 
long,  swimming  by  means  of  four  paddles, 
—  literally  the  Sea-Serpents  of  the  era. 
The  remains  of  the  head  of  one,  from  the 
banks  of  the  river  Meuse  in  Holland 
(whence  the  name),  are  represented  in  Fig. 
331.  The  American  rocks  have  afforded 
forty  species  of  these  Mosasaurs.  The  head 
of  the  largest  was  four  feet  long,  and  the 
mouth  was  hence  of  enormous  size.  Be- 
sides, it  had  a  joint  in  the  lower  jaw,  either 
side,  in  place  of  the  usual  suture  (at  a,  in 
Fig.  332),  which  enabled  the  two  sides  of  a 
jaw,  as  the  bones  (rami)  were  not  united  at 
their  extremities,  to  act  like  a  pair  of  arms, 
in  working  down  the  immense  throat  any 
large  animal  it  might  undertake  to  swallow 
whole.  A  tooth  of  one  of  the  Mosasaurs, 
half  the  natural  size,  is  shown  in  Fig.  333. 

Among  more  modern  kinds  of  Eeptiles 

,  -I  ~  ,.,  i    m       ,  i  « 

there  were  Crocodiles  and  Turtles;  one  of 
the  latter,  from  Kansas,  15  feet  in  breadth, 
according  to  Cope,  between  the  tips  of  the  extended  flippers. 


Tooth  of  Mosasaurus  prin- 


194  MESOZOIC   TIME.  —  REPTILIAN  AGE. 

The  Birds  of  the  American  Cretaceous  included  Divers, 
Cormorants,  Waders,  and  two  which  had  pointed  teeth  like 
a  Eeptile,  and  probably,  as  Marsh  the  discoverer  suggests,  a 
long  tail,  like  the  bird  of  Solenhofen  (page  178). 

3.    General  Observations. 

1.  Geography.  —  In  North  America  the  position  of  the  Cre- 
taceous beds  along  the  borders  of  the  Atlantic  south  of  New 
York,  near  the  Mexican  Gulf,  and  also  over  a  large  part  of 
the  Bocky  Mountain  region,  indicates  that  these  border  re- 
gions and  a  large  part  of  the  Western  Interior  were  under 

Pig.  334. 


North  America  iuthe  Cretaceous  Period ;  MO,  Upper  Missouri  region. 

water  when  the  period  opened,  as  represented  in  the  above 
map  (Fig.  334).  The  shaded  part  of  the  continent  exhibits 
the  extent  to  which  it  was  submerged.  (This  map  should  be 


CRETACEOUS  PERIOD.  195 

compared  with  that  on  page  73.)  It  shows  that  the  Chesa- 
peake and  Delaware  gulfs  were  in  the  ocean;  that  Florida 
.was  still  under  water ;  that  the  region  of  the  Missouri  Kiver 
was  a  salt-water  region ;  that  the  Eocky  Mountain  region  was 
largely  submerged.  This  mountain  region  was  in  some  parts 
at  least  10,000  feet  lower  than  now,  the  Cretaceous  beds  hav- 
ing this  elevation  upon  it.  The  Mexican  Gulf  spread  over 
a  large  part  of  Georgia,  Alabama,  and  Mississippi,  extended 
northward  to  the  mouth  of  the  Ohio,  and  then,  west  of 
Missouri  and  Kansas,  stretched  far  north  over  the  present 
slopes  of  the  great  Western  mountains,  reaching  perhaps  to 
the  Arctic  Ocean,  though  on  this  point  the  evidence  is  not  yet 
decisive.  The  deposits,  excepting  those  of  Texas,  appear  to 
be  of  sea-shore  and  off-shore  formations ;  the  Texan  compact 
limestones  were  probably  formed  in  clear  interior  waters. 

In  Europe  the  Chalk  appears  to  have  been  accumulated  in 
an  open  sea,  where  the  water  was  some  hundreds  of  feet  deep. 
The  material  of  the  Chalk  has  been  stated  on  page  187  to  be 
mainly  the  shells  of  Ehizopods,  and  that  of  the  associated  flint 
to  have  been  derived  largely  from  Diatoms  and  Sponges. 
Rhizopods,  Diatoms,  and  Sponges  are  now  living  in  many 
parts  of  the  ocean,  over  the  bottom,  even  where  the  depth  is 
thousands  of  feet ;  and  the  Rhizopods  are  making  chalk-like 
accumulations  of  vast  area.  There  are,  hence,  in  the  present 
seas,  the  conditions  requisite  for  making  chalk,  and  also  flint. 
The  fossils  of  the  Chalk  are  in  many  regions  turned  into  flint, 
and  some  hollow  specimens  are  filled  with  quartz  crystals,  or 
agate. 

2.  Climate.  —  The  corals  and  other  tropical  life  of  the  rocks 
indicate  that  the  British  seas  were  at  least  warm-temperate 
to  latitude  60°  north.  On  the  American  side  the  temper- 
ature of  the  waters  appears  to  have  been  cooler,  as  it  now 
is,  in  corresponding  latitudes ;  and  still  it  was  considerably 
warmer  than  the  present.  The  warm  oceanic  zone  which 
spread  over  the  British  seas  appears,  from  the  distribution  of 
the  fossils,  to  have  reached  the  North  American  coast  south 


196  MESOZOIC  TIME. 

of  Long  Island,  and  probably  had  no  place  on  the  coast  north 
of  Cape  Hatteras.  The  plants  of  the  Upper  Missouri  region 
indicate  a  warm-temperate  climate  over  that  territory. 

GENERAL  OBSERVATIONS  ON  THE  MESOZOIC. 

1.  Time-Ratios.  —  The  ratios  between  the  Paleozoic  ages  as 
to  the  length  of  time  that  elapsed  during  their  progress,  or 
their  time-ratios,  are  stated  on  page  143  as  probably  not  far 
from  4:1:1.     By  the  same  method,  it  follows  that  the  ratio  for 
the  time  of  the  Paleozoic  and  Mesozoic  was  nearly  4:1;  and 
for  the  Triassic,  Jurassic,  and  Cretaceous  periods,  1 :  1| :  1. 
That  is,  Mesozoic  time  was  about  one  fourth  as  long  as  the 
Paleozoic;  and  the  three  periods  of  the  Mesozoic  were  not 
far  from  equal,  the  Jurassic  being  one  quarter  the  longest. 

2.  American  Geography.  —  On  page  159  it  is  remarked  that 
the  Mesozoic  formations  were  confined  to  the  Atlantic  and 
Gulf-border  regions,  and  to  an  interior  region  west  of  the 
Mississippi  covering  much  of  the  Rocky  Mountain  area,  and 
that  the  intervening  portion  of  the  continent  had  probably 
become  part  of  the  dry  land.     The  facts  which  have  been 
presented  in  the  preceding  pages  have  sustained  this  state- 
ment.    The  Triassico-Jurassic  beds,  as  has  been  shown,  lie  in 
long  narrow  strips  between  the  Appalachians  and  the  coast, 
and  spread  widely  over  the  Rocky  Mountain  region  and  west 
nearly  to  the  Pacific.     The  Cretaceous  beds  cover  the  Atlantic 
and  Gulf  borders,  and  also,  like  the  Triassic,  a  very  large  part 
of  the  slopes  of  the  Rocky  Mountains  and  the  Pacific  border 
west  of  the  Sierra  Nevada.     The  eastern  half  of  the  continent 
during  the  Mesozoic  was,  therefore,  receiving  rock-formations 
only  along  its  borders,  while  the  western  half  had  marine 
deposits  in  progress  over  its  great  interior  and  on  the  ocean's 
border. 

The  American  Mesozoic  deposits,  for  the  most  part,  do  not 
bear  evidence  that  they  were  formed  in  a  deep  ocean.  They 
appear  to  have  accumulated  mainly  along  coasts,  or  in  shallow 


REPTILIAN  AGE.  197 

waters  off  coasts,  or  in  shallow  inland  seas ;  the  Cretaceous 
limestone  of  Texas  indicates  a  pure  sea,  like  that  required  for 
coral-reefs,  but  not  necessarily  one  of  great  depth. 

The  Appalachians  —  the  eastern  mountains  of  the  continent 

—  had  nearly  their  present  elevation  before  the  early  Meso- 
zoic  beds  commenced  to  form  (page  157).     But  the  region  of 
the  Eocky  Mountains  —  the  western  chain  —  was  to  a  great 
extent  still  a  shallow  sea  even  during  the  Cretaceous  period, 
or  when  the  Mesozoic  era  was  drawing  to  its  close  (page  194). 

Only  one  series  of  mountain-elevations  can  be  pointed  out, 
with  our  present  knowledge,  as  originating  in  Eastern  North 
America  in  the  course  of  the  Mesozoic  era,  although  great 
oscillations  of  level  were  much  of  the  time  in  progress.  This 
one  is  that  of  the  Mesozoic  red  sandstone  and  trap  along  the 
Atlantic  border  region,  as  explained  on  page  181. 

On  the  western  side  of  the  continent  the  mountain-making 
after  the  Jurassic  was  on  a  far  grander  scale,  the  Sierra  Nevada, 
Wahsatch,  and  other  high  ranges  dating  from  this  epoch. 

3.  European  Geography.  —  Europe  has  its  Mesozoic  rocks 
distributed  in  patches,  or  in  several  independent  or  nearly 
independent  areas,  which  show  that  it  retained  its  condition 
of  an  archipelago  throughout  Mesozoic  time.  The  oscillations 
of  level,  as  indicated  by  the  variations  in  the  rocks,  —  varia- 
tions both  as  to  the  nature  of  the  beds  and  their  distribution, 

—  were  more  numerous  and  irregular  than  in  North  America. 
The  mountain-elevations  formed,  however,  were  few  and  small 
compared  with  those  that  followed  either  the  Paleozoic  or 
the  Mesozoic  era.     One  series  of  disturbances  is  referred  to 
the  close  of  the  Triassic,  and  another  to  that  of  the  Jurassic. 

Among  the  Mesozoic  formations  of  the  European  continent 
there  are  deposits  of  all  kinds,  —  those  of  sea-shores  ;  of  off- 
shore shallow  waters  ;  of  inland  seas ;  of  moderately  deep 
oceanic  waters;  and  of  marshy,  or  dry  and  forest-covered 
land. 

Both  in  America  and  Europe  there  were  some  coal-beds 
made,  though  of  small  extent  compared  with  those  of  the 
Carboniferous  age. 


198  MESOZOIC  TIME. 

4.  Life.  —  The  Mesozoic  era  witnessed  —  (1)  the  decline  of 
some  ancient  or  Paleozoic  types  of  both  plants  and  animals, 
(2)  the  increase  and  culmination  of  mediaeval  or  Mesozoic 
types,  and  (3)  the  beginning  of  some  of  the  most  important 
of  modern  or  Cenozoic  types. 

7.  Disappearance  of  Ancient  or  Paleozoic  features.  —  Among  the 
ancient  tribes  of  plants,  the  Catamites,  or  Tree-rushes,  and 
several  genera  of  Ferns,  disappear  in  the  Jurassic.  Among 
the  old  Brachiopod  tribes,  the  Spirifer  and  Leptcena  families 
end  in  the  Triassic ;  among  higher  Mollusks,  the  Silurian  type 
of  Orthoceras,  and  Devonian  of  Goniatites,  have  their  last 
species  in  the  Triassic ;  in  Fishes,  the  Ganoids  lose  the  verte- 
brated  feature  of  their  tails,  characterizing  them  in  the  Paleo- 
zoic, in  the  same  period,  and  thus  bear  evidence  of  progress. 

2.  Progress  in  Mesozoic  features.  — The  Cycads,  among  plants, 
were  those  most  characteristic  of  the  Mesozoic :  they  after- 
ward yielded  to  other  kinds,  and  now  are  nearly  an  extinct 
tribe.  The  Cephalopods,  among  Mollusks,  existed  in  vast 
numbers,  both  those  with  external  shells,  as  the  Ammonites, 
and  those  without,  as  the  Belemnites.  The  whole  number  of 
species  of  Cephalopods  now  known  from  the  Mesozoic  forma- 
tions is  nearly  1,200.  Of  these,  about  950  were  of  the  Nau- 
tilus and  Ammonite  families.  No  Ammonite  now  exists,  and 
the  only  chambered  species  which  are  now  living  are  2  or  3  of 
the  genus  Nautilus.  The  whole  number  of  species  of  Cephal- 
opods living  in  the  course  of  the  Mesozoic  era  may  have  been 
three  or  four  times  1,200,  since  only  a  part  would  have  been 
preserved  as  fossils.  The  sub-kingdom  of  Mollusks,  therefore, 
culminated  in  the  Mesozoic  era ;  for  its  highest  order,  that  of 
the  Cephalopods,  was  then  at  its  maximum. 

The  type  of  Eeptiles  was  another  that  expanded  and  reached 
its  height,  —  that  is,  its  maximum  in  number,  variety,  and 
rank  of  species,  —  and  commenced  its  decline  in  the  Mesozoic 
era. 

There  were  huge  swimming  Saurians,  Enaliosaurs,  in  the 
place  of  whales  in  the  sea ;  bat-like  Saurians  or  Pterodactyls 


KEPTILIAN  AGE.  199 

flying  tlirough  the  air ;  four-footed  Saurians,  both  grazing  and 
carnivorous,  many  of  them  25  to  50  feet  long,  occupying  the 
marshes  and  estuaries ;  great  biped  Saurians  or  Dinosaurs 
over  the  land ;  and  snake-like  Mosasaurs  in  the  ocean,  some 
having  the  great  length  of  75  or  80  feet. 

In  the  era  of  the  Wealden  and  Lower  Cretaceous  there  lived, 
in  and  about  Great  Britain,  4  or  5  species  of  Dinosaurs  20  to 
50  feet  long,  10  to  12  Crocodilians,  Lizards,  and  Enaliosaurs 
10  to  50  feet  long,  besides  Pterodactyls  and  Turtles;  arid 
many  more  than  this,  since  all  that  lived  would  not  have  left 
their  remains  in  the  deposits.  To  appreciate  this  peculiarity 
of  mediaeval  time,  it  should  be  considered  that  in  the  present 
age  Britain  has  no  large  Eeptiles ;  in  Asia  there  are  only  two 
species  over  15  feet  in  length;  in  Africa  but  one;  in  all 
America  but  three ;  in  the  whole  world  not  more  than  six ; 
and  the  largest  of  the  six  does  not  exceed  25  feet  in  length. 
North  America,  during  the  Cretaceous,  appears  to  have  ex- 
ceeded all  the  world  beside  in  the  number  and  size  of  its  Rep- 
tiles. The  Mesozoic  era  is  well  named  the  Age  of  Reptiles. 

All  the  Mesozoic  animals,  excepting  the  Mammals,  belong 
to  the  oviparous  divisions ;  and  the  Mammals  were  mainly 
Marsupial  species,  —  that  is,  semi-oviparous  Mammals,  as  ex- 
plained on  page  50,  —  species  quite  in  harmony,  therefore, 
with  the  other  life  of  the  era.  The  Birds  of  the  age,  or  at 
least  some  of  them,  partook  of  the  Reptilian  features  of  the 
time,  having  long  tails  like  the  associated  Reptiles  (though 
feathered  tails),  with  other  peculiarities  of  the  scaly  tribes ; 
and  some  even  had  reptile-like  teeth.  The  long-tailed  birds 
and  Pterodactyls  were  the  flying  creatures  of  the  age ;  the 
Ichthyosaurs  and  Plesiosaurs,  and  the  like,  the  "  great  whales  " ; 
the  Teleosaurs,  Iguanodon,  and  other  gigantic  species  of  the 
estuaries  and  marshes,  the  creeping  species.  These,  along 
with  the  small  Marsupials  of  the  Cycadean  and  Coniferous 
forests,  were  the  more  prominent  kinds  of  Mesozoic  life. 

3.  Introduction  of  Cenozoic  features.  —  Among  plants  the 
first  of  Angiosperms  (or  the  order  including  all  trees  having 


200  MESOZOIC  TIME. 

a  bark  excepting  the  Conifers,  as  the  Oak,  Maple,  Apple,  etc.), 
and  the  first  of  Palms  are  found  in  the  Cretaceous.  These 
become  the  characteristic  plants  of  Cenozoic  time. 

Among  Vertebrates  there  was  a  great  expansion,  if  not  the 
first,  of  the  great  order  of  Teliost  or  Osseous  Fishes,  the  species 
characteristic  of  earlier  time  having  been  either  Selachians 
(Shark  tribe),  Ganoids,  or  Placoderms  (page  111).  The  first 
of  the  modern  genus  of  Crocodilus  occurs  in  the  Jurassic ;  the 
first  of  Birds  in  the  Triassic  or  Jurassic,  —  the  Eeptilian 
Birds ;  the  first  of  Mammals  in  the  Triassi^  •*—  Marsupials,  or 
semi-oviparous  Mammals.  \  v\ 

Of  the  classes  of  Vertebrates,  Fishes  andTReptiles  commence 
in  the  middle  and  later  Paleozoic,  and)  Birds  and  Mammals 
in  the  early  or  middle  Mesozoic.  .  «J 

Extermination  of  life  at  the  close  of  tie  Cretaceous.  —  At  the 
close  of  the  last  period  of  the  MepoaMc  era  —  the  Cretaceous 
—  there  was  an  extermination  of  Species  over  a  large  part  of 
the  Continental  seas  as  complete  as  that  closing  the  Paleozoic 
era.  In  Europe,  Asia,  and  Eastern  North  America  no  Cre- 
taceous species  have  bee^fJdnm  fossil  in  any  Tertiary  strata. 
In  the  Rocky  Mountain  >re<m>n  and  the  Pacific  border  it  is 
probable  that  some  Cretac&jurs  species  continued  on  into  the 
Tertiary,  as  stated  beyond  (page  209).  There  is  no  reason  for 
asserting  that  the  species  of  tjhe  open  ocean  were  exterminated ; 
on  the  contrary,  it  is  believed  that  at  least  one  Cretaceous 
Mollusk  —  a  Terebratula  —  still  exists  in  the  depths  of  the 
Atlantic. 

Besides  the  destruction  of  species,  there  was  the  final  ex- 
tinction of  several  families  and  tribes.  The  great  family  of 
Ammonites^  and  many  others  of  Mollusks,  all  the  genera  of 
Reptiles  excepting  Crocodilus,  and  others  in  all  departments 
of  life,  came  to  their  end  at  the  close  of  the  Cretaceous  or 
soon  after. 

Extermination  over  so  wide  a  range  of  Continental  seas 
must  have  been  due  to  a  cause  which  acted  as  widely,  and 
no  other  appears  to  be  sufficient  excepting  a  change  of  climate 


CENOZOIC  TIME.  201 

in  the  north.  The  Arctic  and  other  high-latitude  regions 
may  have  been  elevated  more  than  those  of  lower  latitudes, 
for  Tertiary  rocks  do  not  occur  on  the  eastern  borders  of  the 
American  continent  north  of  the  parallel  of  42°  N.  to  show 
that  the  continent  was  then  below  its  present  level.  Con- 
nected with  the  elevation  of  the  land  to  the  north  there  may 
have  been  an  exclusion  of  warm  oceanic  currents  from  the 
Arctic  seas ;  for  in  Behring  Straits  the  depth  of  water  is  less 
than  200  feet.  By  these  means  a  semi-glacial  epoch  may  have 
been  occasioned  which  sent  cold  oceanic  currents  from  the 
north  along  the  sea-borders  and  Continental  seas  to  the  south. 
Should  the  cold  winds  and  cold  oceanic  currents  of  the  north- 
ern part  of  the  existing  temperate  zone  penetrate  for  a  single 
year  into  the  tropical  regions,  they  would  produce  a  general 
extermination  of  the  plants  and  animals  of  the  land,  and  also 
of  those  of  the  coast  and  sea-borders,  as  far  as  the  cold  oceanic 
currents  extended.  A  change  to  a  climate  no  colder  than  the 
present  would  have  been  sufficient  probably  for  all  the  de- 
struction that  took  place,  since  the  life  of  the  Cretaceous  seas, 
even  in  Northern  Europe,  was  largely  that  of  the  warm-tem- 
perate zone. 

While  the  emergence  of  northern  lands  here  appealed  to 
may  have  taken  place  as  the  Cretaceous  period  closed,  there 
appears  to  have  been  no  mountain-making  of  much  extent 
until  the  Tertiary  age  had  already  far  advanced  (page  218). 


IV.  —  CENOZOIC   TIME. 

1.  Age  of  Mammals.  —  Cenozoic  time  covers  two  ages :  1. 
THE  TERTIARY  AGE,  or  AGE  OF  MAMMALS  ;  and  2.  THE  QUATER- 
NARY, or  AGE  OF  MAN. 

2.  General  characteristics,  —  In  the  transition  to  this  era  the 
life  of  the  world  takes  on  a  new  aspect.     Trees  of  modern 
types  —  Oak,  Maple,  Beech,  etc.,  and  Palms  —  unite  with 


202  CENOZOIC  TIME. 

Conifers  to  make  the  forests ;  Mammals  of  great  variety  and 
size,  —  Herbivores,  Carnivores,  and  others,  successors  to  the 
small  semi-oviparous  Mammals,  tenant  the  land  in  place  of 
Reptiles ;  Birds  and  Bats  possess  the  air  in  place  of  reptilian 
Birds  and  Pterodactyls;  Whales  and  Teliost  or  common 
Fishes,  with  Sharks,  mainly  of  modern  type,  occupy  the 
waters  in  place  of  Enaliosaurs,  and  almost  to  the  exclusion 
of  the  ancient  tribes  of  Cestraciont  Sharks  and  Ganoids. 
Finally  Man  appears  when  Mammals  were  passing  their 
maximum  in  grade  and  magnitude,  and  becomes  the  domi- 
nant species  of  the  finished  world. 

I.   TERTIARY  AGE,   or  AGE   OF   MAMMALS. 

The  Mammals  of  this  age  are  all  extinct  species,  and  the 
other  species  of  life  mostly  so ;  the  number  of  living  species 
of  Invertebrates  (Eadiates,  Mollusks,  and  Articulates)  varies 
from  perhaps  one  per  cent  in  the  early  part  of  the  period  to 
90  in  the  latter.  In  the  Quaternary  the  Mammals  of  the 
earlier  part  are  nearly  all  of  extinct  species ;  the  Invertebrates 
are  almost  wholly  of  living  species,  not  over  5  per  cent  being 
extinct. 

I .  Periods. 

The  Tertiary  strata  have  been  divided  by  Lyell  into  three 
groups : 

1.  Eocene  (from  the  Greek  770)9,  dawn,  and  Kaivos,  recent) : 
species  nearly  all  extinct. 

2.  Miocene  (from  fjL€icovt  less,  and  icawos) :  less  than  half 
the  species  living. 

3.  Pliocene  (from  TrXetW,  more,  and  KCLIVO*;)  :  more  than 
half  the  species  living. 

These  subdivisions  are  not  necessarily  those  marked  off 
by  the  grander  physical  changes  of  a  continent. 
In  North  America  there  was  :  — 
1.  The  Lignitic  period,  corresponding  to  the  Lower  Eocene. 


TERTIARY  AGE.  203 

The  beds  follow  on  conformably  after  the  Cretaceous ;  and 
then,  as  the  period  closed,  these  Lignitic  strata,  along  with 
the  underlying  Cretaceous,  were  together  upturned,  folded  into 
mountains,  and  partly  rendered  metamorphic ;  and  this  hap- 
pened both  in  the  Rocky  Mountain  region  and  in  California. 
This  mountain-making  epoch  makes  a  natural  ending  of  the 
period. 

2.  The  Alabama  period,  corresponding  to  the  Middle  and 
Upper  Eocene.     The   beds  in  the   Eocky  Mountain  region 
overlie  nearly  or  quite   horizontally  the  upturned  Lignitic 
and  Cretaceous  beds.     On  the  Gulf  of  Mexico  they  include 
the  marine  beds  of  Claiborne,  Alabama,  and  of  Jackson  and 
Vicksburg,  Mississippi.     The  close  of  the  period  was  marked 
off  by  a  change  over  the  lower  part  of  the  Mississippi  Valley 
about  the  Gulf;   for   no  marine  Tertiary  strata  later  than 
Eocene  exist  in  those  regions.     The  country  in  the  line  of 
Florida  to  the  northwest,  now  300  to  700  feet  above  the  sea- 
level,  is  the  western  boundary  of  the  area  of  the  later  Ter- 
tiary. 

3.  Yorktown,  or  that  of  the  beds  of  Yorktown,  Virginia,  in 
which  20  to  40  per  cent  of  the  species  are  living,  —  usually 
called  Miocene,  but  possibly  including  part,  at  least,  of  the 
Pliocene. 

A  fourth  has  been  separated  as  Pliocene,  or  the  Sumter 
epoch,  based  on  observations  on  the  beds  in  Sumter  and  Dar- 
lington districts,  South  Carolina ;  but  according  to  Conrad,  it 
may  not  be  distinct  from  the  Yorktown. 

2.    Rocks:   Kinds  and  Distribution. 

The  beds  are  either  of  marine  or  of  fresh-water  origin. 

The  marine  Tertiary  beds  of  North  America  border  the 
continent  south  of  New  England  along  both  the  Atlantic 
Ocean  and  the  Mexican  Gulf,  overlying  the  Cretaceous  in 
part.  The  most  northern  locality  is  on  Martha's  Vineyard. 
(See  map,  page  69,  in  which  the  area  is  lined  obliquely  from 
the  left  above  to  the  right  below.)  They  spread  northward 


204  CENOZOIC  TIME. 

to  the  mouth  of  the  Ohio,  and  also  westward  into  Texas,  west 
of  the  Mexican  Gulf. 

The  marine  Tertiary  beds  do  not,  like  the  Cretaceous, 
stretch  north  and  northwest  up  the  eastern  slopes  of  the 
Eocky  Mountains ;  but,  instead,  there  are  over  these  slopes 
extensive  fresh-water  Tertiary  strata  (formed  in  and  about 
great  lakes),  with  in  many  places  some  of  the  lowest  beds  of 
brackish-water  origin,  as  shown  by  the  fossils.  This  fresh- 
water Tertiary  extends  over  the  summit  region  of  the  Eocky 
Mountains;  and  there  the  lower  part  includes  not  only 
brackish-water,  but  also  salt-water,  beds,  along  with  those 
of  fresh-water  formation.  Marine  Tertiary  occurs  also  in 
California  and  Oregon,  not  far  from  the  coast. 

The  Lignitic  period,  or  early  Eocene,  includes  the  marine 
and  brackish-water,  and  associated  fresh-water,  strata  of  the 
Upper  Missouri  and  Eocky  Mountain  regions.  They  are  re- 
markable for  containing  extensive  beds  of  good  mineral  coal, 
called  brown  coal  or  lignite,  whence  the  name  of  the  period. 
These  coal-beds  are  worked  at  Evanston,  Coalville,  and  other 
places  on  or  near  the  Central  Pacific  Eailroad.  In  Colorado 
and  New  Mexico  the  Lignitic  Tertiary  passes  downward, 
according  to  the  statements  of  some  observers,  into  lignitic 
strata  that  belong  to  the  Upper  Cretaceous. 

Lignitic  beds  underlying  the  marine  Tertiary  of  the  Missis- 
sippi Valley  south  of  the  Ohio  are  also  of  this  era. 

The  Alabama  period,  or  the  Middle  and  Later  Eocene, 
comprises  the  marine  Tertiary  of  the  Gulf  border  from  Mis- 
sissippi eastward,  and  the  lower  beds  of  the  Tertiary  forma- 
tion along  the  Atlantic  border. 

To  the  Yorktown  period,  or  Miocene,  belong  the  marine  Ter- 
tiary beds  of  the  Atlantic  border  from  New  Jersey  to  South 
Carolina,  overlying  the  Eocene  ;  and  fresh-water  strata  of  great 
extent  in  the  Upper  Missouri  region  and  elsewhere  over  the 
eastern  slopes  of  the  Eocky  Mountains. 

The  Pliocene  Tertiary,  besides  including  possibly  marine 
beds  in  South  Carolina,  as  mentioned  above,  comprises  fresh- 


TERTIARY  AGE.  205 

water  beds  in  the  Upper  Missouri  region,  and  to  the  south, 
where  they  overlie  the  Miocene  fresh-water  strata,  and,  like 
them,  are  of  lacustrine  origin. 

The  Tertiary  rocks  are  generally  but  little  consolidated; 
they  consist  mostly  of  compacted  sand,  pebbles,  clay,  earth 
that  was  once  the  mud  of  the  sea-bottom  or  of  estuaries, 
mixed  often  with  shells,  or  are  such  kinds  of  deposits  as  now 
form  along  sea-shores  and  in  shallow  bays  and  estuaries,  or 
in  shallow  waters  off  a  coast.  There  are  also  limestones 
made  of  shells,  and  others  of  corals,  resembling  the  reef- 
rock  of  coral  seas.  The  latter  are  found  mainly  in  the  States 
bordering  on  the  Mexican  Gulf.  Another  variety  of  rock  is 
buhrstone,  a  cellular  siliceous  rock,  flinty  in  texture,  used,  on 
account  of  its  being  so  hard  and  at  the  same  time  full  of 
irregular  cavities,  for  making  millstones.  It  is  found  in 
South  Carolina  and  Alabama. 

The  Tertiary  of  Great  Britain  occurs  mostly  in  the  south- 
eastern part  of  England,  in  the  London  basin  as  it  is  called, 
and  on  the  southern  and  eastern  borders  of  the  island,  adjoin- 
ing the  Cretaceous. 

On  the  continent  of  Europe  the  Paris  basin  is  noted  for  its 
Eocene  strata  and  fossil  Mammals.  Other  Tertiary  areas  are 
those  of  the  Pyrenean  and  Mediterranean  regions,  those  of 
Switzerland,  of  Austria,  etc.  Some  of  the  marine  Fig.  335. 
Eocene  beds  contain  Ehizopods  (p.  59)  having 
the  shape  of  a  coin,  called  Nummulite  (from 
the  Latin  nummus,  a  coin).  One  is  here  figured, 
of  natural  size ;  it  has  the  exterior  of  half  of 
it  removed  to  show  the  cells  within.  Occasion- 
ally  the  beds  are  so  far  made  up  of  these  Nummulites  that 
the  rock  is  called  Nummulitic  limestone. 

These  marine  Eocene  strata  spread  very  widely  over  Eu- 
rope, Northern  Africa,  and  Asia,  —  occurring  in  the  Pyre- 
nees, forming  some  of  their  summits ;  in  the  Alps  to  a  height 
of  10,000  feet ;  in  the  Carpathians,  in  Algeria,  in  Egypt,  where 
the  most  noted  pyramids  are  made  of  Nummulitic  limestone, 


206  CENOZOIC   TIME. 

in  Persia,  in  the  Western  Himalayas  (the  region  of  Cash- 
mere), to  a  height  of  16,500  feet.  The  later  Tertiary  forma- 
tions are  much  more  limited  in  distribution,  and  many  are  of 
terrestrial  or  fresh-water  origin. 

The  rocks  are  similar  to  those  of  North  America,  but  in- 
clude more  of  hard  sandstone  and  limestone.  The  sandstone 
is  a  very  common  building-stone  in  different  parts  of  Europe, 
being  soft  enough  to  be  worked  with  facility,  yet  generally 
hardening  on  exposure,  owing  to  the  fact  that  it  contains  cal- 
careous particles  (triturated  shells),  which  render  the  perco- 
lating waters  or  rain  calcareous,  so  that  on  evaporating  they 
produce  a  calcareous  deposit,  as  a  cement,  among  the  grains 
of  sand. 

The  Eocene  formation  of  Southeastern  England  consists  of 
beds  of  clay  and  sand,  the  lowest  of  sand  sometimes  contain- 
ing rolled  flints.  The  Lower  Eocene  includes  the  Thanet 
sands,  Woolwich  beds,  and  London  clay ;  the  Middle  Eocene, 
the  lower  Bagshot  beds ;  the  Upper  Eocene,  the  Barton  clay, 
Bembridge  beds,  and  the  Hempstead  beds  near  Yarmouth. 
The  Older  Pliocene  includes  the  Coralline  crag  and  Eed  crag 
of  Suffolk ;  and  the  Newer  Pliocene,  the  Norwich  crag,  which 
is  of  fluvio-marine  origin.  No  marine  Miocene  beds  have 
yet  been  identified  in  Great  Britain. 

I.    Life. 
1.    Plants. 

The  great  feature  of  the  Tertiary  vegetation  is  the  preva- 
lence of  Angiosperms,  the  tribe  of  plants  which  made  its  first 
appearance  in  the  Cretaceous.  Leaves  of  Oak,  Poplar,  Maple, 
Hickory,  Dogwood,  Mulberry,  Magnolia,  Cinnamon,  Fig,  Syca- 
more, Willow,  and  many  others,  have  already  been  found  in 
both  American  and  European  Tertiary  strata,  besides  the  re- 
mains of  Palms  and  Conifers.  A  leaf  of  a  Tertiary  Fan-palm 
(species  of  Sabal),  found  in  the  Upper  Missouri,  must  have 
been,  when  entire,  12  feet  in  breadth.  Nuts  are  also  common 
in  some  beds,  —  as  at  Brandon,  Vermont.  Fig.  336  is  the 


TERTIARY   AGE. 


207 


leaf  of  an  Oak ;  Fig.  337,  of  a  species  of  Cinnamon ;  Fig.  338, 
of  a  Palm ;  Fig.  339,  the  nut  of  a  beech,  closely  like  that  of 


Figs.  336-340. 


Fig.  336,  Quercus  myrtifolia?;  337,  Cinnamomum  Mississippiense ;  338,  Calamopsis  Danac; 
339,  Fagus  ferruginea?;  340,  Carpolithes  irregularis. 

the  common  beech ;  Fig.  340,  another  nut,  from  Brandon,  of 
unknown  relations.  Figs  341-346 

The  Eocene  Plants  of  Great 
Britain  included  Palms,  and 
among  those  of  Central  and  South- 
ern Europe  there  were  many  spe- 
cies related  to  the  trees  of  Austra- 
lia; while  the  Miocene  and  Plio- 
cene had  much  similarity  to  those 
of  America. 

The  microscopic  plants  which 
form  siliceous  shells,  called  Diatoms  (Figs.  341  to  346,  all 


Diatoms. 


208 


CENOZOIC  TIME. 


greatly  enlarged),  make  extensive  deposits  in  some  places. 
One  stratum  near  Kichmond,  Virginia,  is  30  feet  thick,  and 
is  many  miles  in  extent ;  another,  near  Monterey,  California,  is 
50  feet  thick,  and  the  material  is  as  white  and  fine  as  chalk, 
which  it  resembles;  another,  near  Bilin  in  Bohemia,  is  14 
feet  thick.  The  material  from  the  latter  place  was  used  as  a 
polishing-powder  (and  called  Tripoli,  or  polishing-slate)  long 
before  it  was  known  that  its  fine  grit  was  owing  to  the  re- 
mains of  microscopic  life.  Ehrenberg  has  calculated  that  a 
cubic  inch  of  the  fine  earthy  slate  contains  about  forty-one 
thousand  millions  of  organisms.  Such  accumulations  of  Dia- 
toms are  made  both  in  fresh  waters  and  salt,  and  those  of  the 
ocean  at  all  depths. 

2.  Animals. 

The  most  prominent  fact  with  regard  to  the  Tertiary  In- 
vertebrates is  their  general  resemblance  to  modern  species. 
Although  a  number  of  the  genera  are  extinct,  and  nearly 
every  Eocene  species,  there  is  still  a  modern  look  in  the  re- 
Pigs.  347-351. 


349 


847 


350 


LAMELLIBRANCHS :  Fig.  347,  Ostrea  sellseformis ;  348,  Crassatella  alta ;  349,  Astarte 
Conradi ;  350,  Cardita  planicosta.  —  GASTEROPOD :  351,  Turritella  carinata. 

mains,  and  the  specimens  have  often  the  freshness  of  a  shell 
from  a  modern  beach. 


TERTIARY  AGE. 


209 


The  preceding  are  figures  of  a  few  Mollusks  of  the  marine 
Eocene,  from  Claiborne  Alabama.  Fig.  347  represents  an 
Eocene  Oyster ;  Fig.  348,  a  species  of  Crassatella  ;  Fig.  349,  an 
Astarte;  Fig.  350,  a  Cardita  ;  and  Fig.  351,  a  Turritella. 

Figs.  352  to  355  are  species  of  Miocene  shells,  from 
Virginia ;  figs.  352,  353  represent  a  very  common  Crepidula, 

Figs.  352-355. 

354 


GASTEROPOD  :  Figs.  352,  353,  Crepidula  costata.  —  L AMELLIBRANCHS  :  Fig.  354, 
Yoldia  liinatula ;  355,  Callista  Sayana. 

upper  and  under  sides.  The  species  of  the  epoch  include  the 
common  Oyster  and  Clam,  and  other  modern  species ;  and 
these  are,  therefore,  among  the  most  ancient  of  living  species 
on  the  globe.  The  Lignitic  beds  of  the  Kocky  Mountain 
region  in  Wyoming  Territory  and  elsewhere  contain  a  very 
few  Cretaceous  species,  among  them  the  Inoceramus  proble- 
maticus. 

With  regard  to  Vertebrates  the  points  of  special  interest 
are  the  following  :  — 

1.  In  the  class  of  Fishes :  (1)  The  prevalence  of  Teliosts, 
or  fishes  allied  to  the  Perch  and  Salmon,  as  already  stated ; 
and  (2)  the  abundance  of  Sharks,  some  of  them  having  teeth 
6  inches  long  and  broad.  The  teeth  of  sharks  are  the  durable 
part  of  the  skeleton ;  they  are  very  abundant  in  both  Eocene 
and  Miocene  beds.  Fig.  356  represents  a  tooth  of  the  Car- 
charodon  angustidens.  The  larger  teeth  above  alluded  to  belong 
to  the  Carcliarodon  megalodon,  and  are  found  at  different  places 
on  the  Atlantic  border  from  Martha's  Vineyard  southward. 


210 


CENOZOIC  TIME. 


Figs.  356,  357. 


Fig.  357  represents  the  tooth  of  another  common  kind  of 
Shark,  a  species*  of  Lamna,  from  Claiborne. 

In  the  class  of  Eeptiles :  The  existence  of  numerous  Croco- 
diles and  Turtles.  The  shell  of  one  of  the  Miocene  turtles, 

found  fossil  in  India,  had  a  length  of 
12  feet,  and  the  animal  is  supposed 
to  have  been  20  feet  long.  The  first 
of  true  Snakes,  moreover,  occur  in 
the  Eocene. 

Dinosaurian  remains,  unknown  in 
Europe  above  the  Cretaceous,  occur 
sparingly  in  the  Lignitic  beds  of  the 
Rocky  Mountain  region,  and  have 
strengthened  the  doubt  whether  these 
beds  are  not  part  of  the  Upper  Cre- 
taceous. 

In  the  class  of  Birds  :  The  species 
found  are  not  long-tailed,  or  in  any 
respect  reptilian,  but  resemble  mod- 
ern birds  ;  they  are  related  to  the 
Pelican,  Waders,  Pheasants,  Perchers, 
TEETH  OF  SHARKS. -Fig.  ase,  Cultures  Owls,  Woodpeckers,  and 

Carcharodon    angustidens ;    357,    Other  Kinds. 

In  the  class  of  Mammals :  The 

occurrence  of  the  first  of  Whales,  the  first  of  Carnivores,  Her- 
bivores, Rodents,  Monkeys,  and  of  other  tribes,  indicating  a 
large  population  of  brute  animals,  different  from  the  present 
in  species,  though,  in  general,  related  to  the  modern  kinds 
in  form  and  structure.  A  few,  however,  are  widely  diverse 
from  anything  in  existence,  —  such  combinations  as  the  mind 
would  never  have  imagined  without  aid  from  the  skeletons 
furnished  by  the  strata. 

In  the  early  Eocene  there  appear  to  have  been  more  Her- 
bivores than  Carnivores ;  but  afterward  the  Carnivores  were 
as  common  as  now. 

Cuvier  first  made  known  to  science  the  existence  of  fossil 


TERTIARY  AGE. 


211 


Tertiary  Mammals.  The  remains  from  the  earthy  beds  about 
Paris  had  been  long  known,  and  were  thought  to  be  those  of 
modern  beasts.  But,  through  careful  study  and  comparisons 
with  living  animals,  he  was  enabled  to  bring  the  scattered 
bones  together  into  skeletons,  ascertain  the  tribe  to  wThich 
they  belonged,  and  determine  the  food  and  mode  of  life  of  the 
ancient  but  now  extinct  species.  Cuvier  acquired  his  skill 
by  observing  the  mutual  dependence  which  subsists  between 
all  parts  of  a  skeleton,  and,  in  fact,  all  parts  of  an  animal.  A 
sharp  claw  is  evidence  that  the  animal  has  trenchant  or  cut- 
ting molar  teeth,  and  is  a  flesh-eater ;  a  hoof,  that  he  has  broad 
molars  and  is  a  grazing  species ;  and,  further,  every  bone  has 
some  modification  showing  the  group  of  species  to  which  it 
belongs,  and  may  thus  be  an  indication,  in  the  hands  of  one 
well  versed- in  the  subject,  of  the  special  type  of  the  animal, 
and  of  its  structure,  even  to  its  stomach  within  and  its  hide 
without. 

One  of  these  Paris  beasts  from  the  middle  Eocene  beds  is 
called  a  Paleothere,   from  the  Greek  TraXaio'?,   ancient,  and 
v,  wild  beast.     It  is  related  to  the  modern  Tapirs  (Fig. 


Fig.  358. 


Tapirus  Indicus. 


358),  and  was  of  the  size  of  a  horse.     Another  kind,  called  a 
Xiphodon,  was  of  more  slender  habit,  and  somewhat  resembled 


212 


CENOZOIC   TIME. 


a  stag,  as  shown  in  Fig.  359.  There  were  others,  related  to  the 
hog,  or  Mexican  Peccary ;  also  some  Carnivores,  a  Bat,  and  an 
Opossum. 

Among  American  Eocene  Mammals  there  is  a  species  of 
whale  of  great  length,  called  a  Zeuglodon,  from  %evy\7),  yoke, 
and  oSoi;?,  tooth,  in  allusion  to  the  fact  that  part  of  the  teeth 
have  two  long  prongs  which  give  them  a  yoke-like  shape. 

Fig.  359. 


Xiphodon  gracile. 

The  bones  occur  in  many  places  in  the  Gulf  States,  and  in 
Alabama  the  vertebrae  were  formerly  so  abundant  as  to  have 
been  built  up  into  stone  walls,  or  burned  to  rid  the  fields  of 
them.  The  living  animal  was  probably  70  feet  in  length. 
One  of  the  larger  vertebrae  measures  a  foot  and  a  half  in  length 
and  a  foot  in  diameter. 

The  Lignitic  beds,  or  early  Eocene  of  North  America,  have 
afforded  no  Mammalian  remains.  But,  from  the  overlying 
Middle  or  Later  Eocene,  of  the  Green  Kiver  basin,  near  Fort 
Bridger,  a  large  number  of  species  have  been  obtained.  The 
skull  of  one  kind,  of  elephantine  size,  having  six  horn-cores, 
and  called  by  Marsh  Dinoceras,  in  allusion  to  its  horns,  is  rep- 
resented in  Fig.  360.  It  was  somewhat  related  to  the  Khino- 
ceros.  There  were  also  the  earliest  of  the  Horse  tribe,  called 
Orohippus;  and  it  is  remarkable  that  these  Eocene  Horses 
had  four  usable  toes  (Fig.  361)  instead  of  the  one  only  of  the 


TERTIARY  AGE. 


213 


modern  Horse.     The  relations  in  the  foot  of  the  latter  to  dif- 
ferent kinds  of  Tertiary  Horses  are  illustrated  in  Figs.  361-364. 

Fig.  360. 


Dinoceras  miraMle  (  x  £). 

In  Fig.  364  it  is  shown  that  the  modern  Horse  has  one 
usable  toe,  the  third,  and  rudiments  of  two  others,  the  second 


Figs.  361-364. 
362 


w 


FEET  OF  SPECIES  OF  THE  HORSE  TRIBE.  -Fig.  361,  Orohippus,  of  The  Eocene 
(x  |);  362,  Anchitherium,  of  the  Miocene;  363,  Hipparion,  of  the  Pliocene;  364,  the 
modern  Horse. 


214 


CENOZOIC  TIME. 


and  fourth,  in  what  are  called  the  splint-bones.  In  the  Hip- 
parion,  of  the  Pliocene  (Fig.  363),  the  second  and  fourth  have 
hoofs,  but  they  are  not  usable.  In  Anchitherium,  of  the  Mio- 
cene (Fig.  362),  the  second  and  fourth  toes  come  to  the  ground, 
and  are  therefore  usable.  In  Orohippus  (Fig.  361)  there  are 
four  toes,  the  second,  third,  fourth,  and  fifth,  and  all  are  usable. 

Other  Wyoming  species  are  related  to  the  Tapir  and  Hog, 
some  approaching  in  characters  the  Paris  Paleothere.  There 
were  also  Monkeys,  some  Carnivores  related  to  the  Cat  and 
Wolf,  Bats,  Squirrels,  Moles,  and  Marsupials. 

The  Miocene  beds  of  the  "  Bad  Lands  "  on  the  White  River, 
in  the  Upper  Missouri  region  and  elsewhere  in  the  West,  have 


afforded  remains  of  other  Mammals. 

Tig.  365. 


Among  them  are  several 


Tooth  of  Titanotherium  Proutii  (X 

Carnivores  related  somewhat  to  the  Hyena,  Dog,  and  Panther  ; 
many  Herbivores,  including  Rhinoceroses,  species  approaching 
the  Tapir,  Peccary,  Deer,  Camel,  Horse;  Rodents.  Fig.  365 


Fig.  366. 


Teeth  of  Rhinoceros  (Hyracodon)  Nebrascensis. 

represents  a  tooth,  half  the  natural  size,  of  a  Titanothere,  an 
animal  related  to  the  Tapir  and  Paleothere,  but  of  elephan- 
tine size,  standing  probably  7  or  8  feet  high.  Fig.  366  repre- 


TERTIARY  AGE. 


215 


sents  a  few  of  the  teeth  of  an  animal  related  to  the  Rhinoceroses. 
Another  species,  the  Brontotherium,  nearly  as  large  as  an 
Elephant,  but  related  somewhat  to  the  Ehinoceros,  had  a  pair 
of  great  horns. 

Pig.  367- 


Fig.  368. 


Oreodon  gracilis. 

Fig.  367  represents  the  skull  of  another  Miocene  Mammal, 
called  an  Oreodon,  which  is  intermediate  between  the  Deer, 
Camel,  and  Hog.  Remains  of  a 
Camel  and  Rhinoceros,  and  some  of 
the  tapir-like  beasts,  have  been 
found  in  the  Miocene  of  the  Atlan- 
tic border. 

In  the  Pliocene  beds  of  the 
Upper  Missouri  region  still  other 
species  occur;  including  Camels,  a 
Rhinoceros,  an  Elephant,  a  Masto- 
don, Horses,  Deers,  a  Wolf,  a  Fox, 
a  Tiger,  —  a  range  of  species  quite 
Oriental  in  character. 

Among  Mammals  of  the  Euro- 
pean Miocene  there  were  Elephants,  Mastodons,  Deer,  and 


Dinotherium  giganteum  (X 


216 


CENOZOIC   TIME. 


other  Herbivores,  many  Carnivores,  Monkeys,  Ant-eaters,  etc. 
One  of  the  most  singular  species  is  the  Dinothere,  the  form 
of  the  skull  of  which  is  shown  in  Fig.  367 ;  its  actual  length 
is  3  feet  8  inches.  It  appears  to  have  had  a  proboscis  like 
an  Elephant,  but  the  tusks  proceeded  from  the  lower  instead 
of  upper  jaw,  and  were  bent  downward. 

The  earliest  of  the  Bovine  or  Ox  group  occur  in  the  Euro- 
pean Pliocene. 

4.  General  Observations. 

1.  Geography.  —  The  Tertiary  period  completed  mainly  the 
work  of  rock-making  along  the  borders  of  the  continent,  which 

Pigs.  369. 


Map  of  North  America  in  the  early  part  of  the  Tertiary  Period. 

had  been  in  progress  during  the  Cretaceous  period.  The  ac- 
companying map  shows  approximately  the  part  of  the  conti- 
nent of  North  America  under  the  sea  toward  the  middle  of 


TERTIARY   AGE.  217 

the  Eocene  Tertiary,  or  when  the  Lignitic  period  was  near  its 
close.  By  comparing  it  with  the  map  of  the  Cretaceous  con- 
tinent, page  194,  it  is  seen  that  in  the  interval  the  Kocky 
Mountain  region  had  become  dry  land.  The  occurrence  of 
brackish-water  beds  in  the  Lignitic  Tertiary  of  the  Upper 
Missouri  region,  and  of  salt-water  beds,  as  well  as  brackish- 
water,  in  the  Lignitic  of  the  summit  of  the  mountains,  indicate, 
as  shown  by  Hayden,  that  the  passage  from  the  marine  condi- 
tion of  the  Cretaceous  era  gradually  changed  into  that  of  the 
fresh-water  lakes  and  dry  land  of  the  later  Eocene.  The 
gradualness  of  the  transition  is  further  shown  in  the  occur- 
rence of  Lignitic  or  coal-bearing  beds  in  the  Upper  Creta- 
ceous. After  the  Eocene,  the  elevation  went  forward,  but 
still  with  extreme  slowness,  for  in  the  Miocene  the  eastern 
slopes  of  the  mountains  were  covered  with  immense  fresh- 
water lakes,  whose  borders  were  the  haunts  of  the  Mammals 
of  the  era ;  and  these  lakes  were  continued,  though  of  dimin- 
ished size,  into  the  Pliocene.  The  Cretaceous  beds  are  now 
10,000  feet  above  the  sea-level,  showing  that  this  amount  of 
elevation  has  taken  place  since  that  era ;  but  this  height  may 
not  have  been  fully  attained  before  the  closing  part  of  the 
Pliocene  period.  The  area  of  the  Mississippi  river-system, 
embracing  the  slopes  of  the  Eocky  Mountains  on  the  west 
and  those  of  the  Appalachians  on  the  east,  then  for  the  first 
time  attained  its  full  dimensions.  The  Mexican  Gulf  was 
much  larger  in  the  Eocene  period  than  at  present ;  but  there 
was  not  that  long  extension  northward  which  it  had  during 
the  Cretaceous  period.  Florida  was  still  submerged,  and  also 
all  the  bays  of  the  Atlantic  coast  south  of  New  York.  After 
the  Eocene  epoch  the  Mexican  Gulf  became  much  more  con- 
tracted by  an  elevation  of  the  coast  along  the  Gulf,  accom- 
panying which  the  part  of  Georgia  northwest  of  Florida, 
where  Eocene  and  Cretaceous  beds  had  been  formed  in  the 
sea,  was  raised  300  to  700  feet  above  the  sea-level.  By  the 
close  of  the  Tertiary  period  the  continent  appears  to  have 
reached  nearly  its  present  outline. 
10 


218  CENOZOIC  TIME. 

Besides  the  gradual  changes,  there  was  in  the  Bocky  Moun- 
tain region  and  also  in  California  the  making  of  mountain 
ranges.  At  the  close  of  the  Lignitic  period  there  were  up- 
turnings  of  the  Lignitic  and  Cretaceous  formations,  both  to- 
gether, and  high  ridges  in  Colorado,  Utah,  and  Wyoming  are 
part  of  the  results  of  the  disturbances.  Probably  at  the  same 
time  the  Cretaceous  strata  of  California,  west  of  the  Sierra 
Nevada,  were  made  into  mountains  that  are  now  part  of 
the  coast  ranges.  This  was  then  one  of  the  great  mountain- 
making  epochs  in  American  Geological  history. 

In  the  Orient  the  Eocene  era  was  one  of  very  extensive 
submergence  of  the  land,  as  shown  by  the  distribution  of  the 
nummulitic  beds  over  Europe,  Asia,  and  Northern  Africa,  as 
stated  on  page  205.  Before  the  close  of  the  Eocene,  the 
greater  part  of  these  Continental  seas  became  dry  land,  and 
in  general  continued  so  afterward ;  for  the  marine  Miocene  and 
Pliocene  are,  comparatively,  of  limited  extent.  Many  of  the 
great  mountains  of  the  globe,  as  the  Pyrenees,  Alps,  Carpa- 
thians, Himalayas,  etc.,  received  then  a  large  part  of  their 
elevation,  as  is  proved  by  their  containing  Eocene  rocks  in 
their  structure,  or  by  their  bearing  them  about  their  summits. 
Thus  it  is  learned  that  the  elevation  of  the  Pyrenees,  though 
commenced  before  the  close  of  the  Cretaceous,  was  mainly 
produced  in  the  middle  or  later  part  of  the  Eocene,  as  also 
that  of  the  Julian  Alps,  the  Apennines  and  Carpathians,  and 
that  of  heights  in  Corsica.  The  Himalayas,  in  their  western 
part  about  Cashmere,  have  nummulitic  or  Eocene  beds,  at  a 
height  of  16,500  feet ;  so  that  even  this  great  chain,  although 
earlier  elevated  to  the  east,  was  not  completed  before  the 
Middle  Eocene ;  and  even  later  than  this  it  received  a  consid- 
erable part  of  its  elevation,  as  later  Tertiary  beds  at  lower 
levels  show.  The  elevation  of  the  Western  Alps,  including 
Mont  Blanc,  is  referred  by  Elie  de  Beaumont  to  the  close  or 
latter  part  of  the  Miocene  period;  and  that  of  the  Eastern 
Alps,  along  the  Bernese  Oberland,  to  the  close  of  the  Plio- 
cene. An  elevation  of  3,000  feet  took  place  in  Sicily  after 
the  Pliocene. 


QUATERNARY  AGE.  219 

Many  parts  of  the  region  of  the  Andes  were  raised  3,000 
to  5,000  feet  or  more  in  the  course  of  the  Tertiary  period. 

Climate.  —  In  Europe,  the  fact  that,  during  the  Eocene, 
Palms  abounded  in  Britain,  is  evidence  of  a  sub-tropical  or 
warm-temperate  climate  even  in  its  northern  latitudes. 

The  plants  of  the  Miocene  in  Southern  Europe  are  supposed 
to  indicate  a  sub-tropical  climate  there  during  the  middle 
Tertiary,  but  England  had  lost  its  palms  and  was  cooler. 

In  North  America,  the  Eocene  palms  and  other  plants  of 
the  Upper  Missouri  region  show  that  the  temperature  now 
found  in  the  Dismal  Swamp  in  North  Carolina  characterized 
in  the  Early  Tertiary  era  the  region  of  the  Upper  Missouri, 
the  vicinity  of  the  Great  Lakes,  and  also  Vermont,  where  ex- 
ists the  Brandon  deposit  of  nuts  and  lignite. 

The  Camels,  Ehinoceroces,  and  other  animals  of  the  Pliocene 
of  the  Upper  Missouri,  seem  to  prove  that  a  warm-temperate 
climate  still  prevailed  there  in  that  closing  epoch  of  the  Ter- 
tiary period. 

It  is  therefore  plain  that  the  Earth  had  not  as  great  a  diver- 
sity of  zones  of  climate  as  now ;  and  that  Europe  was  little  if 
any  colder  in  the  Eocene  than  in  the  Jurassic  era.  If  the 
interval  between  the  Cretaceous  and  Tertiary  was  one  of  un- 
usual cold,  through  Arctic  and  other  elevations,  as  suggested 
on  page  200,  the  cold  epoch  had  mostly  passed  when  the 
Eocene  era  opened. 

II.    QUATERNARY   AGE,    or   ERA   OF   MAN. 

1.  General  characteristics.  —  The  Quaternary   age  was   re- 
markable (1)  for  high-latitude  movements  and  operations  both 
north  and  south  of  the  equator ;  (2)  for  the  culmination  of  the 
type  of  brute  Mammals  ;  and  (3)  for  the  appearance  of  Man  on 
the  globe. 

2.  Periods.  —  The  periods  are  three  :  — 

1.  The  Glacial,  or  the  period  when,  over  the  higher  latitudes, 
the  continents  underwent  great  modifications  in  the  features 
of  the  surface  through  the  agency  of  ice. 


220  CENOZOIC   TIME. 

2.  The  Champlain,  when  the  ice  disappeared,  and  the  same 
high-latitude  portions  of  the  continent,  and  to  a  less  extent 
the  lower,  were  below  their  present  level,  and  became  covered 
by  extensive  fluvial  and  lacustrine  formations,  and  along  sea- 
coasts  by  marine  formations. 

3.  The  Recent  or  Terrace  period,  begun  by  a  raising  of  the 
land  nearly  or  quite  to  its  present  level. 

I.  Glacial  Period. 

The  special  effects  of  the  operations  that  went  forward  in 
the  Glacial  period  are  the  following  :  — 
•   1.  Transportation.  —  The  transportation  of  a  vast  amount 
of  earth  and  stones  from  the  higher  latitudes  to  the  lower, 
over  a  large  part  of  the  breadth  of  a  continent. 

The  material  consisted  of  earth,  gravel,  and  stones,  and  also 
in  some  places  broken  trunks  or  branches  of  trees.  Part  of  it 
was  deposited  in  a  pell-mell  or  unstratijied  condition  during  the 
progress  of  the  period,  and  part,  either  stratified  or  unstratified, 
in  the  opening  part  of  the  next  period  when  the  ice  melted. 

This  transported  material  is  called  Drift.  Over  the  interior 
of  the  continent  it  contains  no  marine  fossils  or  relics.  At 
bottom  there  is  often  a  bed  of  clay,  called  bowlder-clay,  be- 
cause large  stones  or  bowlders  often  occur  in  it. 

New  England,  Long  Island,  Canada,  New  York,  and  the 
States  west  to  Iowa  are  in  many  parts  thickly  covered  with 
this  northern  unstratified  Drift.  It  reaches  south  to  the  lati- 
tude of  39°,  or  nearly  to  the  southern  limits  of  Pennsylvania, 
Ohio,  Indiana,  Illinois,  and  Central  Missouri,  being  rarely 
traceable  south  of  the  Ohio  Eiver.  Over  the  western  half  of 
the  continent,  west  of  the  meridian  of  98°  W.,  the  northern 
drift  is  mostly  wanting. 

Besides  this  northern  Drift,  there  are  similar  accumulations 
of  earth  and  stones  belonging  to  the  same  era,  distributed  lo- 
cally about  some  of  the  Appalachian  ridges,  south  of  Drift 
latitudes ;  also  on  a  grand  scale  about  the  higher  ridges  of  the 
summit  of  the  Eocky  Mountains,  and  in  the  Sierra  Nevada 
and  other  ranges  and  heights  of  the  Pacific  border  region. 


QUATERNARY  AGE.  221 

The  stones  are  of  all  dimensions,  from  that  of  a  small  peb- 
ble to  masses  as  large  as  a  moderate-sized  house.  One  at 
Bradford  in  Massachusetts  is  30  feet  each  way,  and  its  weight 
is  estimated  to  be  at  least  4,500,000  pounds.  Many  on  Cape 
Cod  are  20  feet  in  diameter.  One  lying  on  a  naked  ledge  at 
Whitingham  in  Vermont  measures  43  feet  in  length  and  30 
in  height  and  width,  or  40,000  cubic  feet  in  bulk,  and  was 
probably  transported  across  Deerfield  Valley,  the  bottom  of 
which  is  500  feet  below  the  spot  where  it  lies.  There  are 
many  great  bowlders  of  trap  from  50  to  1,000  tons  in  weight 
along  the  western  border  of  the  Triassico-Jurassic  area  in 
Connecticut;  the  line  reaching  to  Long  Island  Sound,  just 
west  of  New  Haven ;  and  others  similar,  of  equal  magnitude, 
occur  farther  south  on  Long  Island. 

The  drift-material  is  coarsest  to  the  north. 

The  directions  in  which  it  travelled  are  in  general  between 
south  westward  and  southeastward,  and  mostly  between  south- 
ward and  southeastward.  The  material  was  carried  south- 
ward across  the  Great  Lakes  and  across  Long  Island  Sound, 
the  land  to  the  south,  in  each  case,  being  covered  with  stones 
from  the  land  to  the  north. 

The  distance  to  which  the  stones  were  transported  in  North 
America,  as  learned  by  comparing  them  with  the  rocks  in 
place  to  the  north,  is  mostly  between  10  and  40  miles,  though 
in  some  cases  over  200  miles. 

2.  Scratches.  —  The  rocky  ledges  over  which  the  drift  was 
borne  are  often  scratched,  in  closely  crowded  parallel  lines,  as 
in  the  following  figure  (Fig.  370).  The  scratchings  or  groov- 
ings  are  sometimes  deep  and  broad  channellings,  and  at  times 
a  yard  or  more  deep  and  several  feet  wide,  as  if  made  by  a 
tool  of  great  size  as  well  as  power.  At  Kowe  in  Massachu- 
setts, on  the  top  of  Mount  Monadnock,  and  in  the  sandstone 
of  East  Haven,  west  of  New  Haven,  Ct.,  the  scratches  are  of 
this  remarkable  character.  The  scratches  occur  wherever  the 
drift  occurs,  provided  the  underlying  rocks  are  sufficiently 
durable  to  have  preserved  them,  arid  they  are  usually  of  great 


222  CENOZOIC  TIME. 

uniformity  in  any  given  region.  In  some  places  two  or  more 
directions  may  be  observed  on  the  same  surface.  They  are 
found  in  the  valleys  and  on  the  slopes  of  mountains  to  a 
height,  on  the  Green  Mountains,  of  4,400  feet,  and  on  the 
"White  Mountains  of  5,500  feet. 

Fig.  370. 


Drift  groovings  or  scratches. 

They  often  cross  slopes  and  valleys  obliquely,  —  that  -is-, 
without  following  the  direction  of  the  slope  or  valley.  But, 
when  so,  it  is  usually  found  that  these  valleys  are  small  tribu- 
taries to  some  greater  valley.  The  scratches  have  a  nearly 
common  course  over  the  higher  levels ;  but  they  generally 
conform  to  the  directions  of  the  great  valleys  of  the  land. 
Thus,  in  the  Hudson  Eiver  Valley,  between  the  Catskills  and 
Green  Mountains,  the  scratches  have  mostly  the  Hudson  River 
course;  so  also  in  the  Connecticut  River  Valley,  the  Merri- 
mack,  and  other  valleys  they  have  the  course  of  the  valley. 

The  stones,  or  bowlders,  are  often  scratched  as  well  as  the 
rocks. 

3.  European  Drift. — The  Drift  in  Europe  presents  the  same 
general  course  and  peculiarities  as  in  North  America.  It 
reaches  south  in  some  places  to  about  latitude  50°.  The 
region  south  of  the  Baltic,  and  parts  of  Great  Britain,  are 
covered  with  drift  and  stones  from  Scandinavia.  The  distance 


QUATERNARY  AGE.  223 

of  travel  varies  from  5  or  10  miles  to  500  or  600.  About  the 
Alps  and  other  high  mountains  south  of  Drift  latitudes  there 
are  local  accumulations  of  Drift  of  the  Glacial  area,  and  also 
scratches  over  the  surface  rocks. 

4.  Fiords.  —  Fiords  are  deep,  narrow  sea-channels  running 
many  miles  into  the  land.     They  occur  on  the  coasts  of  Nor- 
way, Britain ;  of  Maine,  Nova  Scotia,  Labrador,  Greenland ; 
on  the  coast  of  Western  North  America  north  of  the  Straits  of 
De  Fuca;  along  that  of  Western  South  America  south  of 
latitude  41°  S. 

Fiords  are  thus,  like  the  Drift,  confined  to  the  higher  lati- 
tudes of  the  globe,  the  Drift-latitudes  ;  and  the  two  may  have 
been  of  contemporaneous  origin. 

5.  Origin  of  the  Drift  —  Nothing  but  moving  ice  could  have 
transported  the  Drift  with  its  immense  bowlders. 

Glacier  Theory.  —  The  ice  is  performing  this  very  work  now 
in  the  glacier  regions  of  the  Alps  and  other  icy  mountains, 
and  stones  of  as  great  size  have  in  former  times  been  borne 
by  a  slow-moving  glacier  from  the  vicinity  of  Mont  Blanc 
across  the  lowlands  of  Switzerland  to  the  slopes  of  the  Jura 
Mountains,  and  left  there  at  a  height  of  over  2,000  feet  above 
the  level  of  Lake  Geneva.  Moreover,  there  are  in  many 
places  deposits  of  bowlder-clay,  made  of  the  earth  formed  by 
trituration  of  stones  against  stones  during  the  moving  of  the 
glacier.  Further,  there  are  scratches,  of  precisely  the  same 
character  as  to  numbers,  depth,  and  parallelism,  in  the  granitic 
and  limestone  rocks  of  the  ridges ;  and,  besides,  the  transported 
material  is  left  unstratified  over  the  land,  wherever  it  was  not 
acted  upon  and  distributed  by  Alpine  torrents. 

Icebergs  also  transport  earth  and  stones,  as  in  the  Arctic 
seas ;  and  great  numbers  are  annually  floated  south  to  the 
Newfoundland  banks,  through  the  action  of  the  northern  or 
Labrador  current,  where  they  melt  and  drop  their  great  bowlders 
and  burden  of  gravel  and  earth  to  make  deposits  over  the  sea- 
bottom.  But  icebergs  could  not  have  covered  great  surfaces 
so  regularly  with  scratches ;  and,  again,  there  are  no  marine 


224  CENOZOIC  TIME. 

relics  in  the  unstratified  drift  to  prove  that  the  continent  was 
under  the  sea  in  the  Glacial  period. 

There  is  a  seeming  difficulty  in  the  Glacial  theory,  from  the 
supposed  want  of  a  sufficient  slope  in  the  surface  to  produce 
movement.  But  a  slope  in  the  under  surface  is  not  needed, 
any  more  than  for  the  flowing  of  pitch.  Pitch,  deposited  in 
continued  supply  on  any  part  of  a  plain,  would  spread  in  all 
directions  around ;  and  this  it  would  do  if,  instead  of  a  plain, 
the  surface  beneath  had  an  ascending  slope.  The  slope  of  the 
upper  surface  of  a  plastic  or  fluid  substance  determines  the  rate 
of  flow,  not  that  of  the  under  surface.  Hence,  if  ice  were 
accumulated  over  a  region  so  that  the  upper  surface  had  the 
requisite  slope,  there  would  be  motion  in  the  mass  in  the 
direction  of  this  slope,  whatever  the  bottom  slope  might  be. 
At  the  same  time  the  slope  of  the  land  at  bottom,  or  the  courses 
of  the  valleys,  would  determine  to  some  extent  the  movement 
at  bottom ;  just  as  oblique  grooves  in  a  sloping  board,  down 
which  pitch  was  moving,  would  determine  more  or  less  com- 
pletely the  direction  of  the  movement  of  the  pitch  that  was 
in  the  grooves. 

All  the  facts  or  phenomena  connected  with  the  northern 
Drift  are  fully  explained  by  reference  to  a  great  northern 
semi-continental  glacier  as  the  cause,  and  those  relating  to 
local  drift  in  the  Appalachians,  Rocky  Mountains,  Sierra  Ne- 
vada, Alps,  and  other  high  mountains  south  of  Drift  latitudes, 
on  the  view  that  local  glaciers  covered  these  heights  in  the 
Glacial  period. 

The  height  to  which  scratches  and  drift  occur  about  the 
White  Mountains  proves  that  the  upper  surface  of  the  ice  in 
that  region  was  6,000  or  6,500  feet ;  and  hence  that  the  ice 
wras  not  less  than  5,000  feet  thick  over  Northern  New  Eng- 
land. With  a  thickness  of  even  2,000  feet  the  glacier  would 
have  had  great  abrading  power.  Soft  rocks  would  have  been 
deeply  ploughed  up  by  it,  and  all  jointed  rocks,  soft  or  hard, 
would  have  been  torn  to  fragments,  -and  the  loosened  masses 
borne  off. 


QUATERNARY  AGE.  225 

The  stones  and  earth  transported  by  the  Continental  glacier 
were  gathered  up  by  its  lower  part,  from  the  surface  of  hills 
or  ridges  that  projected  into  it,  and  even  of  the  plains  beneath 
it ;  for  there  were  no  peaks  rising  above  its  upper  surface  to 
be  a  source  of  avalanches,  as  in  the  Alps. 

The  cold  of  the  Glacial  period  was  probably  due  in  part  to 
the  continents  having  at  the  time  a  higher  level  above  the  sea 
over  the  higher  latitudes.  This  would  not  only  produce  greater 
cold  through  the  extension  and  elevation  of  the  lands,  but  also 
through  its  exclusion  of  the  warm  oceanic  currents  of  the 


Atlantic  and  Pacific  from  their  flow  into  the  Arctic  Zone. 

2.  Champlain  Period. 

The  Champlain  period,  as  is  proved  by  marine  relics  and  by 
other  facts  described  beyond,  was  an  era  of  depression  in  the 
continents  over  the  higher  latitudes  below  the  present  level,  and 
a  depression  which,  within  certain  limits,  increased  to  the 
northward.  It  was  also  a  period,  as  indicated  by  the  terres- 
trial life,  of  warmer  climate  than  the  Glacial ;  and,  probably, 
because  of  the  lower  level  of  the  northern  or  high-latitude 
lands.  The  warmer  climate  appears  to  have  determined  the 
melting  of  the  great  glacier,  and  it  caused  this  melting  to  go  on 
widely  over  its  surface ;  so  that,  when  it  had  thinned  down 
the  ice  to  within  500  or  1,000  feet,  the  disappearance  of  the 
rest  of  the  ice  went  forward  with  accelerated  progress. 

(1)  The  melting  was  thus  the  great  event  of  the  opening 
part  of  the  Champlain  period ;  and  it  must  have  caused  im- 
mense floods  in  all  valleys,  vastly  beyond  those  from  the 
breaking  up  of  an  ordinary  winter. 

With  the  melting  of  the  lower  1,000  feet,  and  during  the 
era  of  floods,  there  would  have  been  (2)  the  deposition  of  the 
earth,  gravel,  and  stones  contained  therein;  and  in  the  de- 
position, wherever  the  material  fell  over  the  land,  it  would 
have  gone  down  pell-mell  and  been  left  (a)  unstratifted ;  while, 
whatever  fell  into  flowing  streams,  lakes,  tidal  estuaries,  or 
along  sea-coasts,  would  have  been  (6)  stratified.  The  stratified 
10*  o 


226  CENOZOIC  TIME. 

deposits  of  the  Champlain  period  are  then  either  (1)  of  river- 
valley  origin,  (2)  lacustrine,  or  (3)  estuary  or  marine. 

After  the  era  of  floods  or  the  Diluvial  part  of  the  Champlain 
period,  the  depositions  in  what  may  be  called  the  Alluvial 
part  of  the  period  went  on  more  quietly;  and  many  land 
shells,  bones,  and  other  relics  are  contained  in  the  river- 
valley  deposits  then  made. 

The  Diluvial  beds  consist  of  earth,  clay,  sand  or  pebbles, 
or  of  mixtures  of  these  materials.  And  the  Alluvial  are  partly 
the  same,  but  more  commonly  of  finer  earth  and  clay. 

The  river-border  deposits  occur  in  all  or  nearly  all  the 
river- valleys  within  the  drift  latitudes  of  the  North  American 
continent,  from  Maine  to  Oregon  and  California;  and  they 
exist  farther  south,  extending  along  the  Mississippi  Valley  to 
the  Gulf  of  Mexico.  The  cold  water  descended  the  valley  in 
a  vast  flood  to  the  Gulf,  bearing  on  its  surface  much  drift  ice 
from  the  dissolving  glacier,  —  the  fact  of  the  flood  and  that 
of  the  floating  ice  being  proved,  as  Hilgard  has  shown,  by  the 
nature  of  the  stratified  deposits,  and  the  occurrence  of  northern 
bowlders,  100  to  150  pounds  in  weight  at  least,  as  far  south 
as  the  State  of  Mississippi.  Facts  prove  also  that  the  cold 
waters  and  ice  in  the  Gulf  were  destructive  to  the  tropical 
life  along  its  northern  borders. 

These  river-valley  deposits  form  at  present  elevated  plains 
on  one  or  both  sides  of  the  valley.  Their  elevation  above  the 
river  is  greater  in  Northern  New  England  than  in  Southern ; 
and  there  is  a  like  difference  between  those  of  the  northern 
and  southern  parts  of  the  States  to  the  west  of  New  Eng- 
land. 

The  view  in  Fig.  371  represents  a  scene  on  the  Connecti- 
cut, a  few  miles  below  Hanover  in  New  Hampshire,  where 
there  are  three  different  levels,  or  terraces,  in  the  alluvial 
formation ;  the  upper  shows  the  total  thickness  of  the  for- 
mation down  to  the  river-level. 

Fig.  372  represents  a  section  of  a  valley,  with  the  allu- 
vial formation,  //',  filling  it,  and  the  channel  of  the  river  at  E. 


QUATERNARY  AGE.  227 

Were  the  country  to  be  elevated,  the  river  would  dig  out  a 
deeper  channel  as  the  elevation  went  on,  and  thus  the  top 


Tig.  371. 


Terraces  on  the  Connecticut  River,  south  of  Hanover,  N.  H. 

of  the  valley  formation  would  finally  be  left  far  above  the  river, 
beyond  the  reach  of  its  waters.    The  river  would,  at  the  same 

Fig.  372. 


Section  of  a  valley  in  the  Champlain  epoch,  with  dotted  lines  showing  the  terraces  of  the 

Terrace  epoch. 

time,  wear  away  a  portion  of  this  formation,  either  side,  during 
its  floods,  and  thus  make  room  for  a  lower  flat  on  its  banks, 
over  which  the  flooded  waters  would  spread,  as  illustrated 
by  the  lines  d  df,  b  b',  in  the  figure ;  for  every  river,  not  con- 
fined by  rocks,  has  both  its  low-water  channel  and  its  flood- 
ground. 


228  CENOZOIC  TIME. 

The  lacustrine  deposits  are  of  similar  character  to  those  of 
the  valleys,  and  of  like  distribution  over  the  continent ;  and 
they  are  equally  elevated  above  the  present  level  of  the  water 
they  border. 

The  sea-border  deposils,  or  those  formed  on  sea-shores  and 
estuaries,  are  found  at  many  places  on  the  coasts  of  New  Eng- 
land, both  the  southern  and  eastern.  At  several  localities  in 
Maine  they  afford  shells  at  heights  not  far  from  200  feet 
above  the  sea-level.  They  form  deposits  of  great  thickness 
along  the  St.  Lawrence,  as  near  Quebec,  Montreal,  and  King- 
ston ;  at  Montreal  they  contain  numerous  marine  shells  at  a 
height  of  400  to  500  feet  above  the  river.  They  border  Lake 
Champlain,  being  there  393  feet  in  height  above  its  level; 
and,  besides  marine  shells,  the  remains  of  a  whale  have  been 
taken  from  the  beds. 

In  the  Arctic  regions  similar  deposits  full  of  shells  are 
common,  at  different  elevations  up  to  600  or  800  feet,  and  in 
some  places  1,000  feet,  above  the  sea-level. 

These  sea-border  deposits,  now  elevated,  must  have  been  at 
the  water-level,  or  below  it,  when  they  were  formed ;  that  is, 
in  the  Champlain  period.  The  facts  prove  that  the  river  St. 
Lawrence  was  at  that  time  an  arm  of  the  sea,  of  great  breadth, 
with  the  bordering  land  400  to  500  feet  below  its  present  level; 
that  Lake  Champlain  was  a  deep  lay  opening  into  the  St.  Law- 
rence channel,  and  that  it  had  its  whales  and  seals  as  well  as 
sea-shells ;  that  the  coast  of  Maine  was  in  part  200  feet  or 
more  below  its  present  level,  and  Southern  New  England  40 
feet  or  more. 

The  present  elevated  positions  of  the  river-valley  and  lacus- 
trine formations  over  the  wide  extent  of  the  continent,  from 
the  Atlantic  to  the  Pacific,  are  equally  good  evidence  that 
its  interior,  in  the  Champlain  period,  was  below  its  present 
level. 

There  is  thus  reason  for  believing  that  the  whole  northern 
portion  of  the  continent  was  less  elevated  than  now ;  and  also 
that  the  depression  was  greatest  to  the  north,  since  the  sea- 


QUATERNARY  AGE.  229 

border,  river- valley,  and  lacustrine  formations  are  all  at  higher 
elevations  to  the  north,  or  near  the  northern  boundary  of  the 
United  States,  than  they  are  to  the  south. 

The  facts  here  stated  with  regard  to  elevated  river-valley, 
lacustrine,  and  sea-border  formations  in  North  America  have 
their  parallel  in  Europe.  In  Great  Britain  the  Glacial  period 
was  followed  by  one  of  depression,  in  which  its  northern  por- 
tions were  over  1,000  feet  below  their  present  level.  The  re- 
markable terraces  or  benches  of  Glen  Eoy,  in  Scotland,  are 
three  in  number,  and  1,139,  1,039,  and  847  feet  above  the  sea- 
level.  In  Sweden  there  are  sea-border  beds  with  shells  very 
similar  to  those  of  Maine  and  the  St.  Lawrence.  The  valley 
of  the  Ehine,  and  those  of  many  other  rivers  of  Europe,  have 
their  high  terraces. 

While,  therefore,  the  facts  connected  with  the  Glacial  period 
favor  the  view  that  the  northern  portions  of  the  continents 
were  then  much  raised  above  their  present  level,  those  of  the 
next  or  Champlain  period  prove  that  they  were  afterward 
much  below  their  present  level.  It  hence  appears  that  there 
was  an  upward  high-latitude  movement  for  the  Glacial  period 
and  a  downward  for  the  Champlain  period ;  and  that  the  latter 
movement  brought  to  its  close  the  era  of  ice,  by  occasioning  a 
warm  climate. 

3.  Recent  Period. 

When  the  Champlain  period  was  in  progress,  the  upper 
plain  of  the  sea-border  formations,  now  so  elevated,  was  at  the 
sea-level ;  and  the  high  alluvial  plains  along  the  rivers  were 
the  flood-grounds  of  the  rivers.  The  land  has  since  been  raised ; 
and,  during  the  progress  of  the  elevation,  the  alluvial  forma- 
tions were  cut  into  terraces,  as  represented  in  Fig.  371,  page 
226,  and  the  sea-border  formations,  also,  were  cut  into  other 
terraces,  or  "  benches,"  of  different  levels. 

This  elevation  led  to  the  making  of  terraces  in  the  river- 
valley,  lacustrine,  and  sea-border  Champlain  formations. 

In  Fig.  372  there  are  dotted  lines  showing  the  levels  of  the 


230  CENOZOIC  TIME. 

river  and  its  flood-plain  at  different  periods  in  the  progress 
of  this  elevation ;  and  Fig.  373  represents  the  terraces  com- 
pleted. The  successive  terraces  are  not  necessarily  evidence 
of  as  many  successive  movements  in  the  elevation  of  the 
continent,  yet  may  be  so  in  some  cases. 

Fig.  373. 


Section  of  a  valley  with  its  terraces  completed. 

As  already  stated,  the  river- valley  formations  throughout 
the  continent  are  raised  high  above  the  present  flood-plains 
of  the  rivers  or  lakes,  and  to  a  greater  height  in  the  northern 
portions  of  the  country  than  in  the  southern.  Hence,  while 
the  Champlain  period  was  one  of  a  low  level  in  the  continent, 
especially  at  the  north,  the  Recent  period  began  in  a  rising 
again,  until  the  continent  reached  its  present  height ;  and  this 
rising  was  greatest  at  the  north.  The  facts  seem  hence  to 
sustain  the  conclusion  that  the  high-latitude  oscillations  of 
this  part  of  geological  history  were  an  upward  movement  for 
the  Glacial  period,  a  downward  for  the  Champlain  period,  an 
upward  again  for  the  Recent  period.  There  is  no  evidence 
that  the  movement  resulted  anywhere  in  the  raising  of  a 
mountain-range ;  there  was  simply  a  gentle  bending  upward, 
then  a  sinking,  and  then  a  rising  again  of  the  general  sur- 
face. 

In  Europe  there  was  a  second  Glacial  era,  in  which  the 
northern  portions  of  that  continent  were  again  covered  with 
ice,  and  glaciers  spread  anew  from  the  Alps  over  part  of  Lower 
Switzerland.  It  appears  to  have  occurred  at  the  close  of  the 
Champlain  period,  and  to  have  been  connected  with  the  ris- 
ing of  the  land  that  introduced  the  Recent  period,  —  the 
rising  having  carried  the  land  above  its  present  level.  Proofs 


QUATERNARY   AGE.  231 

of  the  occurrence  of  such  an  epoch  are  found  in  the  remains 
of  the  Reindeer  and  other  sub-arctic  animals,  in  Southern 
France  (page  238),  in  deposits  that  are  subsequent  in  date  to 
true  Champlain  deposits. 

The  Eecent  period  is,  hence,  opened  by  this  second  Glacial 
epoch,  while  it  closes  with  the  modern  or  historical  era. 

Modern  Changes  of  Level. 

The  sea,  the  rivers,  the  winds,  and  all  mechanical  and 
chemical  forces  are  still  working  as  they  have  always  worked ; 
and,  too,  the  earth  is  undergoing  changes  of  level  over  wide 
areas,  although  it  has  beyond  question  reached  an  era  of  com- 
parative repose. 

These  changes  of  level  are  either  paroxysmal,  —  that  is, 
take  place  through  a  sudden  movement  of  the  earth's  crust 
as  sometimes  happens  in  connection  with  an  earthquake ;  or 
they  are  secular,  —  that  is,  result  from  a  gradual  movement 
prolonged  through  many  years  or  centuries.  The  following 
are  some  examples  :  — 

1.  Paroxysmal  —  In  1822  the  coast  of  Western  South 
America,  for  1,200  miles  along  by  Concepcion  and  Valparaiso, 
was  shaken  by  an  earthquake,  and  it  has  been  estimated  that 
the  coast  near  Valparaiso  was  raised  at  the  time  3  or  4  feet. 
In  1835,  during  another  earthquake  in  the  same  region,  there 
was  an  elevation,  it  is  stated,  of  4  or  5  feet  at  Talcahuano, 
which  was  reduced  after  a  while  to  2  or  3  feet.  In  1819 
there  was  an  earthquake  about  the  Delta  of  the  Indus,  and 
simultaneously  an  area  of  2,000  square  miles,  in  which  the 
fort  and  village  of  Sindree  were  situated,  sunk  so  as  to  be- 
come an  inland  sea,  with  the  tops  of  the  houses  just  out  of 
water ;  and  another  region  parallel  with  the  sunken  area,  50 
miles  long  and  in  some  parts  10  broad,  was  raised  10  feet 
above  the  delta.  These  few  examples  all  happened  within 
an  interval  of  sixteen  years.  They  show  that  the  earth  is 
still  far  from  absolute  quiet,  even  in  this  its  finished  state. 


232  CENOZOIC  TIME. 

2.  Secular.  —  Along  the  coasts  of  Sweden  and  Finland,  on 
the  Baltic,  there  is  evidence  that  a  gradual  rising  of  the  land 
is  in  slow  progress.  Marks  placed  along  the  rocks  by  the 
Swedish  government,  many  years  since,  show  that  the  change 
is  slight  at  Stockholm,  but  increases  northward,  and  is  felt 
even  at  the  North  Cape,  1,000  miles  from  Stockholm.  At 
Udde valla  the  rate  of  elevation  is  equivalent  to  3  or  4  feet  in 
a  century. 

In  Greenland,  for  600  miles  from  Disco  Bay,  near  69°  N., 
to  the  frith  of  Igaliko  60°  43'  1ST.,  a  slow  sinking  has  been 
going  on  for  at  least  four  centuries.  Islands  along  the  coast, 
and  old  buildings,  have  been  submerged.  The  Moravian  set- 
tlers have  had  to  put  down  new  poles  for  their  boats,  and 
the  old  ones  stand  "as  silent  witnesses  of  the  change." 

It  is  suspected  that  a  sinking  is  also  in  progress  along 
the  coast  of  New  Jersey,  Long  Island,  and  Martha's  Vine- 
yard, and  a  rising  in  different  parts  of  the  coast-region  be- 
tween Labrador  and  the  Bay  of  Fundy.  There  are  deeply 
buried  stumps  of  forest -trees  along  the  sea-shore  plains  of 
New  Jersey,  whose  condition  can  hardly  be  otherwise  ex- 
plained. 

The  above  cases  illustrate  movements  by  the  century,  or 
those  slow  oscillations  which  have  taken  place  through  the 
geological  ages,  raising  and  sinking  the  continents,  or  at 
least  changing  the  water-line  along  the  land. 

This  fact  is  to  be  noted,  that  these  secular  movements  of 
modern  time  over  the  continents  are,  for  the  most  part,  so  far 
as  observed,  high-latitude  oscillations,  just  as  they  were  in  the 
earlier  part  of  the  Quaternary. 

Life  of  the  Quaternary. 

The  invertebrate  animals  of  the  Quaternary,  and  probably 
also  the  plants,  were  very  nearly  if  not  quite  all  identical 
with  existing  species.  The  shells  and  other  invertebrate 
remains  found  in  the  beds  on  the  St.  Lawrence,  Lake  Cham- 


QUATERNARY   AGE.  — ANIMAL  LIFE.  233 

plain,  and  on  the  coast  of  Maine,  are  similar  to  those  now 
found  on  the  coast  of  Maine  or  Labrador,  or  farther  north. 

The  life  of  the  Quaternary  of  greatest  interest  is  the  Mam- 
malian, which  type,  as  regards  brutes,  culminated  in  the 
Champlain  period.  This  culmination  was  manifested  in  — 
(1)  the  number  of  species,  (2)  the  multitude  of  individuals, 
(3)  the  magnitude  of  the  animals,  —  the  period  in  each  of 
these  particulars  exceeding  the  present  time. 

Along  with  the  brute  Mammals  of  the  Quaternary  ap- 
peared also  Man. 

I.  Brute  Mammals. 

1.  Europe  and  Asia.  —  The  bones  of  Mammals  are  found  in 
caves  that  were  their  old  haunts ;  in  Drift  and  stratified 
Champlain  deposits  along  rivers  and  lakes;  in  sea-border 
deposits ;  in  marshes,  where  the  animals  were  mired ;  in  ice, 
preserved  from  decay  by  the  intense  cold. 

The  caves  in  Europe  were  the  resort  especially  of  the 
Great  Cave-Bear  (Ursus  spelceus),  and  those  of  Britain  of  the 
Cave-Hyena  (Hycena  spelcea).  Into  their  dens  they  dragged 
the  carcasses  or  bones  of  other  animals  for  food,  so  that  relics 
of  a  large  number  of  species  are  now  mingled  together  in 
the  earth,  or  stalagmite,  which  forms  the  floor  of  the  cavern. 
In  a  cave  at  Kirkdale,  England,  portions  of  a  very  large  num- 
ber of  Hyenas  have  been  made  out,  besides  remains  of  an 
Elephant,  Lion,  Tiger,  Bear,  Wolf,  Fox,  Hare,  Weasel,  Elii- 
noceros,  Horse,  Hippopotamus,  Ox,  Deer,  and  other  species,  all 
then  inhabitants  of  that  country.  A  cave  at  Gaylenreuth  is 
said  to  have  afforded  fragments  of  at  least  800  individuals  of 
the  Cave-Bear.  The  Cave-Hyena  is  regarded  as  a  large 
variety  of  the  Hymna  crocuta  of  South  Africa,  and  the  Cave 
Lion,  a  variety  of  Felis  leo,  the  Lion  of  Africa.  But  many  of 
the  species  are  now  extinct. 

The  fact  that  the  numbers  of  species  and  of  individuals  in 
the  Quaternary  was  greater  than  now,  may  be  inferred  from 
comparing  the  fauna  of  Quaternary  Great  Britain  with  that 


234 


CENOZOIC  TIME. 


of  any  region  of  equal  area  in  the  present  age.  The  species 
included  gigantic  Elephants,  two  species  of  Rhinoceros,  a  Hip- 
popotamus, three  species  of  Oxen,  two  of  them  of  colossal  size, 
the  Irish  Deer  (Megaceros  Hibernicus),  whose  height  to  the 
summit  of  its  antlers  was  10  to  11  feet,  and  the  span  of 
whose  antlers  was  in  some  cases  12  feet,  Deer,  Horses,  Wild 
Boars,  a  Wild-cat,  Lynx,  Leopard,  a  Tiger  larger  than  that  of 
Bengal,  a  large  Lion  called  a  Machcerodus,  having  sabre-like 
canines  sometimes  eight  inches  long,  the  Cave-Hyena,  Cave- 
Bear,  besides  various  smaller  species. 

Fig.  374. 


Skeleton  of  Mastodon  giganteus. 


The  Elephant  (Elephas  primigenius)  was  nearly  a  third 
taller  than  the  largest  modern  species.  It  roamed  over 
Britain,  Middle  and  Northern  Europe,  and  Northern  Asia, 
even  to  its  Arctic  shores.  Great  quantities  of  tusks  have 
been  exported  from  the  borders  of  the  Arctic  sea  for  ivory. 


QUATERNARY  AGE.  — ANIMAL  LIFE. 


235 


These  tusks  sometimes  have  a  length  of  12  J  feet.  Near  the 
beginning  of  the  century  one  of  these  Elephants  was  found 
frozen  in  ice  at  the  mouths  of  the  Lena ;  and  it  was  so  well 
preserved  that  Siberian  dogs  ate  of  the  ancient  flesh.  Its 
length  to  the  extremity  of  the  tail  was  16 J  feet,  and  its 
height  9J  feet.  It  had  a  coat  of  long  hair.  But  no  amount 
of  hair  would  enable  an  Elephant  now  to  live  in  those  bar- 
ren, icy  regions,  where  the  mean  temperature  in  winter  is 
40°  F.  below  zero.  Siberia  had  also  a  hairy  Bhinoceros. 

Although  there  were  many  Herbivores  among  the  Qua- 
ternary species  of  the  Orient,  the  most  characteristic  animals 
were  the  great  Carnivores.  The  period  was  the  time  of  tri- 
umph of  brute  force  and  ferocity,  and  the  Orient  was  espe- 
cially the  scene  of  its  triumph. 

2.  North  America.  —  In  the  Champlain  period  there  were 
great  Elephants  and  Mastodons,  Oxen,  Horses,  Stags,  Heavers, 
and  some  Edentates,  "in  Quaternary  North  America,  unsur- 
passed in  magnitude  by  any  in  other  parts  of  the  world. 
Herbivores  were  the  characteristic  type.  Of  Carnivores  there 


Fig.  375. 


Megatherium  Cuvieri  ( x  ^-5-)- 

were  comparatively  few  species ;  no  true  cavern  species  have 
been  discovered.  Fig.  374  (from  Owen)  represents  the  speci- 
men of  the  American  Mastodon  now  in  the  British  Museum. 


236  CENOZOIC  TIME. 

The  skeleton  set  up  by  Dr.  Warren  in  Boston  has  a  height 
of  11  feet  and  a  length  to  the  base  of  the  tail  of  17  feet. 
It  was  found  in  a  marsh  near  Newburgh,  New  York.  The 
American  Elephant  was  fully  as  large  as  the  Siberian. 

3.  South  America.  —  South  America  had,  at  the  same  time, 
its  Carnivores,  its  Mastodons,  and  other  Herbivores;  but  it 
was  most  remarkable  for  its  Edentates,  or  animals  related  to 
the  Sloths. 

Fig.  375  shows  the  form  and  skeleton  of  one  of  these 
animals,  —  the  Megathere.  It  exceeded  in  size  the  largest 
Rhinoceros :  a  skeleton  in  the  British  Museum  is  18  feet 
long.  It  was  a  clumsy,  sloth-like  beast,  but  exceeded  im- 
mensely the  modern  Sloth  in  its  size.  Another  kind  of 
Edentate  had  a  shell  like  a  turtle,  and  was  somewhat  re- 
lated to  the  Armadillo.  One  of  them  is  called  a  Glyptodon 
(Fig.  376).  The  animals  of  this  kind  wrere  also  gigantic,  the 
Glyptodon  here  figured  having  had  a  length,  to  the  extrem- 
ity of  the  tail,  of  nine  feet. 

South  America  was  eminently  the  continent  of  Edentates. 

Pig.  376. 


Glyptodon  clavipes  (X  ^,). 

4.  Australia.  —  Quaternary  Australia,  in  the  Champlain 
period,  contained  Marsupial  animals  almost  exclusively,  like 
modern  Australia ;  but  these  partook  of  the  gigantic  size  so 
characteristic  of  the  Mammalian  life  of  the  period.  One 
species,  called  Diprotodon,  was  as  large  as  a  Hippopotamus, 
and  another,  the  Nototherium,  was  as  large  as  an  ox. 


QUATERNARY  AGE.  — MAN.  237 

5.  Conclusions.  —  The  facts  sustain  the   following   conclu- 
sions :  — 

1.  The  Champlain  period  of  the  Quaternary  was  the  cul- 
minant time  of  Mammals,  both  as  to  numbers  and  magni- 
tude. 

2.  Each  continent  was  gigantic  in  that  type  of  Mammalian 
life  which  is  now  eminently  characteristic  of  it :  The  Orient, 
in  Carnivores,  and,  it  may  be  added,  also  in  Monkeys  ;  North 
America,  in  Herbivores  ;  South  America,  in  Edentates  ;  Aus- 
tralia, in  Marsupials. 

3.  The  climate  of  Great  Britain  and  Europe,  where  were 
the  haunts  of  Lions,  Tigers,  Hippopotamuses,  etc.,  must  have 
been  warmer  than  now,  and  probably  not  colder  than  warm- 
temperate.    The  climate  of  Arctic  Siberia  was  such  that  shrubs 
could  have  grown  there  to  feed  the  herds  of  Elephants,  and 
hence  could  not  have  been  below  sub-frigid,  for  which  degree  of 
cold  it  is  possible  the  animals  might  have  been  adapted  by 
their  hairy  covering. 

4.  The  Champlain  period,  the  meridian  time  of  the  Quater- 
nary Mammals,  was  hence,  as  before  stated,  one  of  warmer 
climate  over  the   continents   than   the   present,  and   much 
warmer  than  that  of  the  Glacial  period.     The  species  may 
have  begun  to  exist  before  the  Glacial  period  ended  in  Eu- 
rope ;    but  they  belonged  pre-eminently  to  the  Champlain 
period,  when  the  sinking  of  the  land  over  the  higher  latitudes 
had  introduced  the  warmer  climate. 

5.  The  larger  part  of  the  great  Mammals  of  the  Quater- 
nary disappeared  with  the  close  of  the  Champlain  period  or 
in  the  early  part  of  the  Recent  period,  while  others  found 
refuge  in  the  tropics.     They  were  animals  of  a  warmer  cli- 
mate than  now  belongs  to  the  regions  which  they  then  inhab- 
ited ;  and  the  cold  of  the  second  Glacial  era,  with  which  the 
Recent  period  opened,  probably  brought  about  the  extermina- 
tion and  forced  migration. 

Such  an  epoch  of  cold  could  not  have  been  passed  through 
by  Europe  without  some  refrigeration  of  the  climate  of  North 


238  CENOZOIC  TIME. 

America,  since  the  two  continents  are  bound  together  by  a 
common  Arctic.  The  remains  of  Eeindeers  have  been  found 
in  Southern  New  York ;  and  they  may  have  been  driven  so 
far  south  by  the  climate  of  that  epoch,  as  the  same  animals 
were  driven,  in  Europe,  to  Southern  France. 

Among  the  Mammals  of  Europe  which  existed  before  the 
close  of  the  Champlain  period,  some  are  now  living ;  as  the 
Reindeer,  Marmot,  Ibex,  Chamois,  Elk,  Wild  Boar,  Goat,  Stag, 
Aurochs,  Urus,  Wolf,  Brown  Bear,  and  others. 

2.  Man. 

1.  Relics  of  Man.  —  The  earliest  relics  of  Man  in  Europe 
are  rude  flint  implements,  as  arrow-heads,  chisels,  etc. ;  flint- 
chippings,  or  the  chips  thrown  off  in  making  the  implements ; 
rude  carvings ;  human  bones  and  skeletons  ;  the  bones  of  the 
animals  used  for  food,  split  lengthwise,  this  being  done  to  get 
at  the  marrow ;  charcoal,  and  other  remains  of  fires.     They 
occur  associated  with  the  remains  of  the  Cave-Bear,  Cave- 
Hyena,  Cave-Lion,  Elephant,  and  other  species.     They  date 
from  the  Champlain  period,  and  perhaps,  in  part,  from  the 
earlier  Glacial  period. 

2.  The  Paleolithic  Era.  —  As  the  only  implements  of  early 
Man  in  Europe  were  of  stone,  the  era  in  human  history  has 
been  called  the  "  Stone  age  "  ;  and  this  earliest  part  of  that 
age,  above  referred  to,  has  t>een  designated  the  Paleolithic 
era,  from  the  Greek  iroXoux?,  ancient,  and  X/#o<?,  stone.     Por- 
tions of  skeletons  referred  to  this  era  have  been  found  in 
Belgium,  and  some  other  countries.     The  Belgian  skulls  are 
"  fair  average  skulls  "  ;  "  the  lowest  yet  discovered  cannot  be 
regarded,"  says  Huxley,  as  "  the  remains  of  a  human  being 
intermediate  between  Man  and  the  Apes."     The  stone  imple- 
ments are  never  polished,  and  are  of  ruder  make  than  those 
of  the  later  part  of  the  Stone  age. 

3.  The  Reindeer  Era,  —  The  second  section  of  the  European 
Age  of  Stone  has  been  called  the  Reindeer  era.     It  was  the 
time  of  the  second  Glacial  epoch,  and  it  is  distinguished  by 


QUATERNARY  AGE.  — MAN.  239 

the  occurrence  of  large  numbers  of  the  bones  of  the  Eein- 
deer  in  the  caves  of  Southern  France,  along  with  the  human 
relics.  The  flint  implements  of  this  era  are  well  made,  but  un- 
polished ;  and  among  the  relics  there  are  implements  of  bone 
or  horn,  and  drawings  of  animals  upon  these  materials.  One 
of  these  drawings  from  Southern  France,  made  on  ivory,  is 
copied  in  Fig.  377.  It  represents  the  hairy  Elephant  of  the 

Fig.  377. 


Elephas  primigenius  ;  engraved  in  ivory  (  X  f ). 

era.  Eemains  of  the  Elephant,  Cave-Bear,  Cave-Hyena,  Cave- 
Lion,  occur  in  the  same  deposits,  and  also  others  of  existing 
species,  as  the  Elk,  Ibex,  Aurochs,  Urus,  etc.  Perfect  skele- 
tons of  man  have  been  found  in  some  of  the  caverns.  Those 
of  Southern  France  are  in  part  of  tall  size,  —  5  feet  9  inches 
to  6  feet,  —  having  well-shaped  heads,  and  a  large  facial  angle 
(85°).  One,  from  a  cave  at  Mentone  (on  the  Mediterranean 
near  the  borders  of  France  and  Italy),  was  of  a  man  full  6  feet 
in  height ;  and  it  lay  buried  in  the  stalagmite  of  the  cave, 
with  flint  implements  and  shell  ornaments  around,  and  a 
chaplet  of  stag's  teeth  across  its  head. 

4.  The  Neolithic  Era,  —  A  third  era  in  the  Stone  age  has 
been  named  the  Neolithic,  from  the  Greek  i/eo?,  new,  and 
X/009.  The  relics  that  tell  us  about  the  man  of  the  era 
are  polished  stone  implements,  broken  pottery,  bones  of  the 
domesticated  dog ;  and  the  fact  that  they  lived  subsequently 


240 


CENOZOIC  TIME. 


to  those  before  described  is  proved  by  the  absence  of  all  re- 
mains of  both  the  extinct  Champlain  Mammals  and  the 
Eeindeer.  These  beds  belong,  therefore,  to  the  Kecent  period, 
after  the  second  Glacial  era  had  passed.  The  human  remains 
in  Denmark  indicate  a  race  like  the  Laplanders  in  many 
respects. 

To  a  time  still  later  in  this  era  belong  the  earlier  "  lake- 
dwellings  "  of  Switzerland,  —  structures  built  out  in  the  lakes 
on  piles.  With  the  oldest  of  them  the  only  implements  are 
of  flint.  But  the  later,  about  the  more  western  Swiss  lakes, 
have  afforded  bronze  implements,  and  belong,  therefore,  to  the 
"  Bronze  age." 

5.  Modern  Human  Relics.  —  In  still  later  deposits,  buried 
coins,  statues,  temples,  cities,  are  found  among  the  earth's 
fossils,  contrasting  strangely  with  the  remains  of  the  species 


Figs.  378,  379. 


378 


379 


Human  skeleton  from  Guadaloupe. 


Conglomerate  containing  coins. 


with  which  the  history  of  the  world's  life  began.  Fig.  379 
represents  a  coin  conglomerate,  containing  coins  of  silver,  of  the 
reign  of  Edward  I.,  found  at  a  depth  of  ten  feet  below  the  bed 


QUATERXAKY  AGE.  — MAN.  241 

of  the  river  Dove  in  England ;  and  Fig.  378,  a  portion  of  a 
human  skeleton  firmly  imbedded  in  a  modern  shell-limestone 
of  Guadaloupe,  the  former  owner  of  which  was  two  centuries 
since  a  fighting  Carib. 

6.  Man  at  the  Head  of  the  System  of  Life.  —  With  the  crea- 
tion of  Man  a  new  era  in  Geological  history  opens.  In  earliest 
time  only  matter  existed,  —  dead  matter.  Then  appeared  life, 
—  unconscious  life  in  the  plant,  conscious  and  intelligent  life  in 
the  animal.  Ages  rolled  by,  with  varied  exhibitions  of  animal 
and  vegetable  life.  Finally  Man  appeared,  a  being  made  of 
matter  and  endowed  with  life,  but,  more  than  this,  partaking 
of  a  spiritual  nature.  The  systems  of  life  belong  essentially 
to  time ;  but  Man,  through  his  spirit,  to  the  opening  and  infinite 
future.  Thus  gifted,  Man  is  the  only  being  capable  of  reach- 
ing toward  a  knowledge  of  himself,  of  nature,  or  of  God.  He 
is,  hence,  the  only  being  capable  of  conscious  obedience  or 
disobedience  of  any  moral  law,  the  only  one  subject  to  degra- 
dation through  excesses  of  appetite  and  violation  of  moral 
law,  the  only  one  with  the  will  and  power  to  make  nature's 
forces  his  means  of  progress. 

Man  shows  his  exalted  nature  in  his  material  structure. 
His  fore-limbs  are  not  made  for  locomotion,  as  in  all  quad- 
rupeds ;  they  are  removed  from  the  locomotive  to  the  cephalic 
series,  being  fitted  to  serve  the  head,  and  especially  the  intel- 
lect and  soul.  Man  stands  erect,  his  body  placed  wholly 
under  the  brain,  to  which  it  is  subservient;  and  his  feet 
are  simply  for  support  and  locomotion,  and  not,  as  in  the 
Monkeys,  grasping  or  prehensile  organs  for  climbing.  His 
whole  outer  being,  in  these  and  other  ways,  shows  forth  the 
divine  feature  of  the  inner  being. 

3.  Extinction  of  Species  in  Modern  Times. 

Species  are  becoming  extinct  in  the  present  era,  as  they 

have  in  the  past.     Man  is  now  a  prominent  means  of  this 

destruction.     The  Dodo,  a  large  bird  looking  like  an  overgrown 

chicken  in  its  plumage  and  wings  (Fig.  380),  was  abundant  in 

11 


242 


CENOZOIC   TIME. 


the  island  of  Mauritius  until  early  in  the  commencement  of 
the  eighteenth  century. 

Fig.  380. 


Dodo,  with  the  Solitaire  in  the  background. 

The  Moa  or  Dinornis  is  a  New  Zealand  bird  of  the  Ostrich 


CENOZOIC  TIME.  243 

kind  that  was  living  less  than  a  century  since ;  it  was  10  or 
12  feet  in  height,  and  the  tibia  ("  drumstick  ")  30  to  32  inches 
long.  In  Madagascar  remains  of  a  still  larger  bird,  but  of 
similar  character,  occur,  called  an  dZpyornis  ;  its  egg  is  over 
a  foot  (13 1  inches)  long.  The  Auk,  a  bird  of  Northern  seas, 
has  become  extinct  within  the  last  25  years ;  the  last  was 
seen  in  1844.  These  are  a  few  of  the  examples  of  the  modern 
extinction  of  species. 

The  progress  of  civilization  tends  to  restrict  forests  and 
forest-life  to  narrower  and  narrower  limits.  The  Buffalo  once 
roamed  over  North  America  to  the  Atlantic,  but  now  lives 
only  on  the  Rocky  Mountain  slopes  west  of  the  Missouri  Eiver. 
The  beaver,  wolf,  bear,  and  wild-boar  were  formerly  common 
in  Britain,  but  are  now  wholly  exterminated. 


GENERAL  OBSERVATIONS  ON  THE  CENOZOIC 

ERA. 

1.  Contrast  between  the  Tertiary  and  Quaternary  ages  in  geo- 
graphical progress.  —  The  review  of  Cenozoic  time  has  brought 
out  the  true  contrast  in  the  results  of  the  Tertiary  and  Qua- 
ternary ages. 

The  Tertiary  carried  forward  the  work  of  rock-making  and 
of  extending  the  limits  of  the  dry  land  southward,  southeast- 
ward, and  southwestward,  which  had  been  in  progress  through 
the  Cretaceous  period,  and,  indeed,  ever  since  Archsean  time. 

The  Quaternary  transferred  the  scene  of  operations  to  the 
broad  surface  of  the  continent,  and  especially  to  its  middle 
and  higher  latitudes. 

Through  the  Tertiary  the  higher  mountains  of  the  globe 
had  been  rising  and  the  continents  extending ;  and  hence  the 
great  rivers  with  their  numerous  tributaries  —  which  are  the 
offspring  of  great  mountains  on  great  continents  —  began  to 
exist  and  to  channel  out  the  mountains  and  make  valleys 
and  crested  heights.  In  the  Glacial  epoch  this  work  went 
forward  with  special  energy.  The  exposed  rocks  yielded 


244  CENOZOIC   TIME. 

"before  the  moving  glacier,  and  the  earth  and  bowlders  formed 
were  taken  up  for  distribution  over  the  continental  surface. 
Torrents,  fed  by  the  melting  ice,  were  also  at  work,  and  with 
even  greater  abrading  power  than  the  ice.  Thus  the  excava- 
tion of  valleys  and  the  shaping  of  hills  and  mountains  were 
everywhere  in  progress.  In  the  Champlain  period,  the  low 
level  at  which  the  land  lay,  and  the  melting  of  the  ice,  with 
the  dropping  of  its  earth  and  stones,  enabled  the  flooded 
streams  to  fill  the  great  valleys  deep  with  alluvium.  In  the 
Eecent  period,  which  followed,  the  upward  movements  of  the 
land  led  to  a  terracing  of  the  Champlain  deposits  along  the 
river- valleys  and  about  the  lakes,  and  completed  the  action 
of  the  rivers  and  vegetation  in  spreading  fertility  over  the 
land. 

Thus,  under  the  rending,  eroding,  and  transporting  power 
of  fresh  waters,  frozen  and  unfrozen,  —  eminently  the  great 
Quaternary  agent,  —  in  connection  with  high-latitude  oscilla- 
tions of  the  earth's  crust,  the  making  of  the  earth  was  finally 
completed. 

2.  Life.  —  In  the  Cenozoic  era,  as  in  the  preceding,  species 
were  disappearing  and  others  took  their  places.  The  Mam- 
mals of  the  early  Eocene  are  different  in  species  from  those 
of  the  later ;  and  these  from  the  Miocene,  the  Miocene  from 
the  Pliocene,  and  the  Quaternary  from  the  Pliocene. 

According  to  the  present  state  of  discovery,  Mammals  com- 
menced in  the  Mesozoic  era,  late  in  the  Triassic  period,  and 
the  Mesozoic  species  were  all  Marsupials.  They  were  the 
precursor  species,  prophetic  of  that  expansion  of  the  new  type 
which  was  to  take  place  after  the  Age  of  Eeptiles  had  closed. 
In  the  early  Eocene,  at  the  opening  of  the  Age  of  Mam- 
mals, appeared  Herbivores  and  Carnivores  of  large  size.  The 
Herbivores  were  mostly  Pachyderms,  related  to  the  Tapir, 
Hog,  and  Ehinoceros,  and  distantly  to  the  Stag.  The  true 
Stag  family  among  Euminants  commenced  in  the  Miocene ; 
the  Elephant  tribe,  in  the  Miocene ;  the  Bovine  or  Ox  family, 
in  the  Pliocene,  or  late  in  the  Tertiary. 


LENGTH  OF  GEOLOGICAL  TIME.  245 


GENERAL  OBSERVATIONS  ON  GEOLOGICAL 
HISTORY. 

1.    Length  of  Geological  Time. 

By  employing  as  data  the  relative  thickness  of  the  forma- 
tions of  the  geological  ages,  estimates  have  been  made  of  the 
time-ratios  of  those  ages,  or  their  relative  lengths  (pages  143, 
196).  These  estimated  time-ratios  for  the  Paleozoic,  Meso- 
zoic,  and  Cenozoic  are  12  :  3  :  1.  But  the  numbers  may 
be  much  altered  when  the  facts  on  which  they  are  based 
are  more  correctly  ascertained.  It  is  quite  certain  that  the 
first  of  the  Paleozoic  ages  —  the  Silurian  —  was,  at  the  least, 
four  times  as  long  as  either  the  Devonian  or  Carboniferous ; 
and  probable  that  Mesozoic  time  was  not  less  than  three 
times  that  of  the  Cenozoic. 

Hence  comes  the  striking  conclusion  that  the  longest  age 
of  the  world  since  life  began  was  the  earliest,  —  when  the 
earth  was  even  without  fishes  and  numbered  in  its  popula- 
tion only  Eadiates,  Mollusks,  and  marine  Articulates.  And 
the  time  of  the  earth's  beginnings  before  the  introduction 
of  life  may  have  exceeded  in  length  all  subsequent  time. 

The  actual  lengths  of  these  ages  it  is  not  possible  to  deter- 
mine even  approximately.  All  that  Geology  can  claim  to  do 
is  to  prove  the  general  proposition  that  Time  is  long.  If  time 
from  the  commencement  of  the  Silurian  included  48  millions 
of  years,  which  some  geologists  would  pronounce  much  too 
low  an  estimate,  the  Paleozoic  part,  according  to  the  above 
ratio,  would  comprise  36  millions,  the  Mesozoic  9  millions, 
and  the  Cenozoic  3  millions. 

One  of  the  means  of  estimating  the  length  of  past  time  is 
that  afforded  by  the  rate  of  recession  of  the  Falls  of  Niagara. 
The  river  below  the  Falls  flows  northward  in  a  deep  gorge, 
with  high  rocky  walls,  for  seven  miles,  toward  Lake  Ontario. 
It  is  reasonably  assumed  that  the  gorge  has  been  cut  out  by 
the  river,  for  the  river  is  annually  making  progress  of  this 


246  HISTORICAL  GEOLOGY. 

very  kind.  From  certain  fossiliferous  Quaternary  beds  over 
the  country  bordering  the  present  walls,  and  other  evidence, 
it  is  proved  that  the  present  gorge,  about  six  miles  long,  was 
made  after  the  middle  of  the  Champlain  period.  The  pres- 
ent annual  progress  of  the  gorge  from  the  cutting  and  under- 
mining action  of  the  waters  has  been  variously  estimated 
from  three  feet  a  century  to  one  foot  a  year.  At  the  larger 
estimate  of  one  foot  a  year,  the  six  miles  would  have  required 
31,000  years ;  or  double  this  if  six  inches  a  year,  as  made  by 
one  observer ;  and  if  the  estimate  be  one  inch  a  year,  or  8| 
feet  a  century,  the  time  becomes  nearly  380,000  years.  The 
calculation  may  be  regarded  as  establishing,  at  least,  the 
proposition  that  Time  is  long,  although  it  affords  no  satis- 
factory numbers.  Other  modes  of  calculation  fully  establish 
this  general  proposition. 

2.  Geographical  Progress  in  North  America. 

The  principal  steps  of  progress  in  the  continent  of  North 
America  are  here  recapitulated :  — 

1.  The  continent  at  the  close  of  the  Archaean  lay  spread 
out  mostly  beneath  the  ocean  (map,  page  73).    Although  thus 
submerged,  its  outline  was  nearly  the  same  as  now.     The  dry 
land  lay  mostly  to  the  north,  as  shown  on  the  map.     The 
form  of  the  main  mass  approximated  to  that  of  the  letter  V, 
and  it  had  a  southeast  and  a  southwest  border  nearly  parallel 
to  its  present  outline. 

2.  Through  the  Paleozoic  ages,  as  the  successive  periods 
passed,  the  dry  land   gradually  extended   itself  southward 
owing  to  a  gradual  emergence  :    that  is,  the   sea-border  at 
the  close  of  the  Lower  Silurian  was  probably  as  far  south 
as  the  Mohawk  Valley  in  New  York  ;  at  the  close  of  the  Upper 
Silurian  it  extended  along  not  far  from  the  north  end  of 
Cayuga  Lake  and  Lake  Erie  ;  and  by  the  close  of  the  Devo- 
nian age  the  State  was  a  portion  of  the  dry  land  nearly  to 
its  southern  boundary.     This  progress  southward  of  the  sea- 


GEOGRAPHICAL  PROGRESS.  247 

border  in  New  York  may  be  taken  as  an  example  of  what 
occurred  along  the  borders  of  the  Archaean,  to  the  west- 
ward. In  other  words,  there  was  through  the  Silurian  and 
Devonian  ages  a  gradual  southerly  extension  of  the  dry  part 
of  the  continent,  —  that  is,  to  the  southeastward  and  the 
southwestward. 

By  the  close  of  the  Carboniferous  age,  or  before  the  opening 
of  the  Mesozoic  era,  the  dry  portion  appears  to  have  so  far 
extended  southwardly  as  to  include  nearly  all  the  area  east  of 
the  Mississippi  and  north  of  the  Gulf  States,  along  with  a  part 
of  that  west  of  the  Mississippi,  as  far  nearly  as  the  western 
boundary  of  Kansas. 

3.  Before  the  Silurian  age  began,  and  in  its  first  period, 
great  subsidences  were  in  progress  along  the  Lake  Superior 
region,  when  the  thick  Huronian   and   Potsdam  formations 
were  made.     The  facts  show  that  the  depression  of  the  lake, 
and  probably   that   of  some   of  the  other  great  lakes,  and 
also  that  of  the   river   St.  Lawrence,  began  to  form   either 
during  the  closing  part  of  the  Archaean  age  or  in  the  early 
part  of  the  Silurian  age. 

4.  During  the  Paleozoic  ages,  rock-formations  were  in  pro- 
gress over  large  parts  of  the  submerged  portions  of  the  conti- 
nent up  to  the  sea-borders,  and  some  vast  accumulations  of 
sand  were  made  as  drifts  or  dunes  over  the  flat  shores  and 
reefs.     These   rock-formations  had  in  general  ten  times  the 
thickness  along  the  Appalachian  region  which  they  had  over 
the  interior  of  the  continent ;  and  they  were  mostly  fragmental 
deposits  in  the  former  region,  while  mostly  limestones  in  the 
latter.     Hence  two  important  conclusions  follow  :  — 

First.  The  Appalachian  region  was  through  much  of  the 
time  an  exposed  shore-reef  or  flat  of  great  extent,  parallel  in 
course  with  the  present  sea-border  as  well  as  that  of  the 
ancient  Archaean  area ;  while  the  interior  was  a  shallow  sea 
opening  southward  freely  into  the  Gulf  of  Mexico,  and  only 
during  some  few  of  the  periods  with  the  same  freedom  east- 
ward directly  into  the  Atlantic.  Most  of  the  western  part 


248  HISTORICAL  GEOLOGY. 

of  the  sea  (west  of  Missouri)  appears  to  have  been  too  deep 
for  deposits  between  the  Lower  Silurian  and  Carboniferous 
eras. 

Secondly.  -The  Appalachian  region  was  undergoing,  through 
the  Silurian  and  Devonian  ages,  great  changes  of  level,  the 
deposits  having  been  made  in  shallow  waters ;  the  region  was 
slowly  sinking,  not  faster  than  the  rate  of  deposition,  and  the 
amount  of  subsidence  exceeded  by  ten  times  that  in  the  In- 
terior Continental  region. 

5.  Of  this  Appalachian  region, -the  Green  Mountain  por- 
tion was  upturned,  rendered  metamorphic,  and  elevated  above 
the  ocean's  level,  at  the  close  of  the  Lower  Silurian;  and 
at  the  same  time  the  valley  of  Lake  Champlain  and  Hudson 
Eiver  was  formed,  if  not  earlier  begun. 

This  valley  and  the  depressions  of  the  Great  Lakes,  and 
also  those  of  the  lakes  extending  in  a  line  through  British 
America  northwestward  from  Lake  Superior  to  the  Arctic 
regions,  lie  not  far  from  the  borders  of  the  Archaean  continent, 
and,  therefore,  between  the  portion  of  the  continent  that  was 
comparatively  stable  dry  land  from  the  time  of  the  Archaean 
onward,  and  that  portion  which  was  receiving  rock-formations 
and  undergoing  oscillations  of  level.  To  this  they  appear  to 
owe  their  origin. 

6.  As  the  Paleozoic  era  closed,  an  epoch  of  revolution  oc- 
curred, in  which  the  rocks  of  the  Appalachian  region  south  of 
New  York  and  west  of  the  Blue  Ridge  underwent  (1)  extensive 
flexures  or  foldings ;  (2)  immense  faultings  in  some  parts ;  (3) 
consolidation,  and,  in  some  eastern  portions,  crystallization 
or  metainorphism,  with  the  loss  of  bitumen  by  the  coal-beds 
changing  them  into  anthracite.     These  changes  affected  the 
region  from  New  York  to  Alabama.     The  effects  of  heat  and 
uplift  were  more  decided  toward,  the  Atlantic  than  toward  the 
interior,  showing  that  the  force  producing  the  great  results 
was  exerted  in  a  direction  from  the  Atlantic  inland,  or  from 
the  southeast  toward  the  northwest.     The  Alleghany  Moun- 
tains were  then  made ;  and  they  were,  consequently,  in  ex- 
istence when  the  Mesozoic  era  opened. 


GEOGRAPHICAL  PROGRESS.          249 

These  mountains  are  parallel  to  the  eastern  outline  of  the 
original  Archaean  continent. 

Similar  changes  may  have  taken  place  on  the  Pacific  side ; 
but  the  facts  thus  far  observed  are  opposed  to  such  a  con- 
clusion. 

This  epoch  of  revolution  was  a  time  of  mountain-making 
also  in  Europe. 

7.  In  the  early  or  middle  Mesozoic  period  (the  continent 
being  largely  dry  land,  as  stated  in  the  latter  part  of  §  2;, 
long  depressions  in  the  surface  of  the  continent,  made  in  the 
course  of  the  Appalachian  revolution  and  situated  between 
the  Appalachians   and   the   sea-border,  were  brackish-water 
estuaries,   or   were   occupied    by   fresh-water    marshes    and 
streams ;  and  Mesozoic  sandstone,  shale,  and  coal-beds  were 
formed  in  them.     The  Connecticut  Valley  region  of  Mesozoic 
rocks  (page  159)  is  one  example.     At  the  same  time  there 
were  formations  in  progress  over  the  Eocky  Mountain  region, 
a  vast  area  from  which  the  sea  was  not  excluded,  or  only  in 
part.     At  the  close  of  the  Jurassic  period,  the  Sierra  Nevada, 
the  Wahsatch,  and  other  great  ranges  on  the  western  side  of 
the  continent  were  made. 

8.  In  the   later   Mesozoic,  or  the   Cretaceous  period,  the 
continent  had  its  Atlantic  and  Gulf  border  yet  under  water, 
and  Cretaceous  rocks  were  formed  about  them,  and  thus  the 
continent  continued  its  former  course  of  enlargement  south- 
eastward (see  map,  page   194).     The   Western  Interior   sea, 
opening  south  into  the  Gulf  of  Mexico,  just  alluded  to,  still 
existed,  and  deposits  were  made  in  it  over  a  very  large  part 
of  the  great  region  reaching  from  Kansas  on  the  east  to  the 
Colorado  on  the  west  and  north  perhaps  to  the  Arctic  Ocean. 
The  Pacific  border  was  also  receiving  an  extension  like  the 
Atlantic. 

9.  In  the  early  Cenozoic,  or  the  Tertiary  age,  the  extension 
of  the  Atlantic  and  Pacific  borders  was  still  continued.     With 
its  close  the  progress  of  the  continent  in  rock -making  south- 
eastward  and   southwestward   was   very  nearly    completed. 


250  HISTORICAL  GEOLOGY. 

After  the  Eocene  era  had  in  part  passed,  or  at  the  close  of 
the  Lignitic  period,  there  was  mountain-making  east  of  the 
Wahsatch,  in  the  Eocky  Mountain  region,  and  west  of  the 
Sierra  Nevada  in  California. 

The  Western  Interior  sea  became  greatly  contracted  after 
this  last  mountain-making  epoch  by  the  progressing  elevation 
of  the  Eocky  Mountain  region,  and  the  Mexican  Gulf  reduced 
greatly  in  size  (map,  page  216).  During  the  middle  of  the 
Eocene  Tertiary,  the  Ohio  and  Mississippi  emptied  into  an 
arm  of  the  Gulf  just  where  they  now  join  their  waters;  at 
the  close  of  the  Eocene  the  Ohio  had  taken  a  secondary  place 
as  a  tributary  of  the  Mississippi.  The  great  Missouri  Eiver, 
the  real  trunk  of  the  Interior  river-system  rather  than  the 
Mississippi,  began  its  existence  after  the  Cretaceous  period, 
and  reached  its  full  size  only  toward  the  close  of  the  Tertiary, 
when  the  Eocky  Mountains  finally  attained  their  full  height. 

10.  The  elevation  of  the  Eocky  Mountains,  like  that  of  the 
Appalachians,  was  the  raising  of  the  land  along  a  region  par- 
allel with  the  outline  of  the  original  Archsean  continent  (see 
map,  page  73).     The  elevation  of  the  Sierra  Nevada  of  Cali- 
fornia was  a  doubling  of  this  same  line  on  the  west ;  while 
the  elevation  of  the  trap  ridges  and  red  sandstone  of  the  early 
Mesozoic  along  the  Atlantic  border  (page  160)  was  a  doubling 
of  the  line  on  the  east ;  finally  the  elevation  of  the  Cretaceous 
with  the  Lignitic  Tertiary  tripled  the  line  of  heights  on  the 
Pacific  side ;  and  the  later  elevation  of  the  Miocene  added  a 
fourth  line  of  heights  to  the  border  of  the  great  Pacific  Ocean. 

11.  The  continent  being  thus  far  completed,  as  the  Qua- 
ternary Age  was  drawing  on,  operations  changed  from  those 
causing  southern   extension  to  those  producing  movements 
of  ice  and  fresh  waters  over  the  land,  especially  in  the  higher 
latitudes ;  and  thereby  valleys,  great  and  small,  were  exca- 
vated over  the  continent ;  earth  and  gravel  were  transported 
and  made  to  cover  deeply  the  rocks  and  spread  the  continent 
with  fertile  plains  and  hills ;  and,  as  the  final  result,  those 
grand  features  and  those  qualities  of  surface  were  educed  that 
were  requisite  to  make  the  sphere  a  fit  residence  for  Man. 


PROGRESS  OF  LIFE.  251 

3.  Progress  of  Life. 

1.  Fact   of   progress   of   life.  —  Life    commenced,    among 
plants,  in  Sea-weeds ;  and  it  ended  in  Palms,  Oaks,  Elms,  the 
Orange,  Rose,  etc.       It  commenced  among  animals  in  Lin- 
gulce  (Mollusks  standing  on  a  stem  like  a  plant),  Crinoids, 

Worms,  and  Trilobites,  and  probably  earlier  in  the  simple  sys- 
temless  Protozoans  (page  59) ;  it  ended  in  Man.  Sea- weeds 
were  followed  by  Lycopods,  Ferns,  and  other  Flowerless  plants, 
and  by  Gymnosperms,  the  lowest  of  Flowering  plants ;  these 
finally  by  the  higher  Flowering  species  above  mentioned,  the 
Palms  and  Angiosperms.  Radiates,  Mollusks,  and  Articulates, 
which  appeared  in  the  early  Silurian,  afterwards  had  Fishes 
associated  with  them;  later,  Reptiles;  later,  Birds  and  in- 
ferior Mammals ;  later,  higher  Mammals,  as  Beasts  of  prey 
and  Cattle ;  lastly,  Man. 

2.  Progress  from  marine  to  terrestrial  life.  —  The  Silurian 
was  eminently  the  marine  age  of  the  world.     The  plants 
found  fossil  in  the  Silurian  until  near  its  close  are  sea-weeds, 
and  the  animals  all  marine.     The  animals  of  the  Devonian, 
also,  are  largely  marine ;  but  there  is  a  step  taken  in  terres- 
trial life  by  the  expansion  of  the  type  of  land-plants,  and  the 
appearance  of  Insects. 

In  the  Carboniferous  age,  and  through  the  Mesozoic  era, 
the  continents,  or  large  areas  over  them,  underwent  alterna- 
tions between  a  submerged  and  a  dry  land  state,  leading  a  kind 
of  amphibian  existence.  The  Carboniferous  age  had,  besides 
its  aquatic  life,  Insects,  Spiders,  Centipedes,  terrestrial  Mol- 
lusks, Amphibian  and  other  Eeptiles,  and  a  great  profusion 
of  forest- trees  and  other  terrestrial  vegetation.  In  the  Meso- 
zoic, to  Reptiles  were  added  Birds  and  Mammals,  eminently 
terrestrial  kinds  of  life. 

The  Cenozoic  was  distinctively  a  continental  era.  The 
continents  became  mostly  dry  land  after  its  earliest  period; 
arid,  as  the  Age  of  Man  approached,  they  had  their  full  size 
and  their  present  diversities  of  surface  and  climate.  With 


252  HISTORICAL   GEOLOGY. 

the  increased  variety  of  conditions  fitted  for  terrestrial  life 
there  was,  beyond  question,  a  great  augmentation  in  the 
number  and  variety  of  terrestrial  species.  Birds  and  Insects 
have  probably  their  greatest  numbers  and  variety  of  species 
in  the  present  age.  Marine  species  still  abound,  but  rela- 
tively to  the  terrestrial  they  are  far  less  numerous  and  less 
extensively  distributed  than  in  the  Mesozoic  and  earlier  ages. 

3.  Progress  was  connected  with  a  constant  change  of  species, 
new  species  appearing  as  others  disappeared.  —  No  species  of 
animal  survived  from  the  beginning  of  life  on  the  globe  to 
the  present  time,  nor  even  through  a  single  one  of  the  several 
geological  ages ;  and  but  few  lived  on  from  the  beginning  of 
any  one  of  the  many  periods  to  its  close,  or  from  one  period 
into  another. 

There  were  widespread  exterminations,  closing  some  of 
the  ages,  as  the  Carboniferous  and  the  Eeptilian ;  there  were 
less  general  exterminations,  closing  the  periods  on  each  of  the 
continents;  and  others,  still  less  general,  at  intermediate 
epochs;  and  often  some  disappearances  accompanied  each 
change  in  the  rock-depositions  that  were  in  progress.  For, 
in  passing  from  one  bed  to  another  above,  some  fossils  fail 
that  occur  below;  and  from  the  strata  of  one  epoch  to  an- 
other, still  larger  proportions  disappear ;  and  sometimes  with 
the  transitions  to  rocks  of  another  period  or  age,  very  nearly 
all  the  species  are  different.  The  rocks  of  the  continents, 
that  are  open  to  examination,  were  made  in  Continental  seas 
and  the  borders  of  the  oceans  adjoining;  and  hence  their 
testimony  with  reference  to  exterminations  does  not  extend 
to  the  Oceanic  areas. 

Of  all  genera  of  animals  now  having  living  species,  only 
one,  the  Molluscan  genus  Discina,  had  species  also  in  the 
earliest  Silurian,  unless  the  Lingulellce,  of  the  Primordial, 
were,  as  formerly  supposed,  true  Lingulce.  Every  other  genus 
of  that  early  time  sooner  or  later  numbered  only  extinct  spe- 
cies. Afterward  in  the  Lower  Silurian,  Nautilus  and  a  few 
others  were  added  to  Discina. 


PROGRESS  OF  LIFE.  253 

Such  unbroken  lines  prove  the  oneness  of  plan  or  system 
through  geological  history. 

Nearly  fifteen  hundred  species  of  Trilobites  have  been 
found  fossil  in  the  Paleozoic  rocks,  and  in  later  formations 
none.  Over  1,000  species  of  the  Ammonite  group  occur  in 
the  Mesozoic  rocks,  —  the  last  then,  or  in  the  early  Tertiary, 
disappeared.  500  species  of  the  Nautilus  tribe  have  been  in 
existence :  now  there  are  but  two  or  three.  Over  1,000  spe- 
cies of  Ganoids  have  been  found  fossil:  the  tribe  is  now 
nearly  extinct.  The  remains  of  2,500  species  of  plants  and 
over  40,000  species  of  animals  have  been  found  in  the  rocks, 
not  one  of  which  is  now  in  existence.  Thus  the  old  has  been 
ever  passing  away.  But  the  number  of  kinds  of  fossils  dis- 
covered cannot  be  the  number  of  species  that  have  existed ; 
and  the  above  numbers  of  marine  species  may  safely  be  mul- 
tiplied by  ten,  and  of  terrestrial  by  a  thousand. 

4.  Progress  not  always  begun  by  the  introduction  of  the  low- 
est species  of  a  group.  —  Mosses,  although  inferior  to  Lycopods 
and  Ferns,  appear  to  have  been  of  later  introduction,  for  no 
remains  have  been  found  in  the  Carboniferous  or  Devonian 
rocks,  although  there  are  relics  of  both  of  the  other  tribes  of 
plants. 

The  earliest  of  Fishes,  instead  of  being  those  of  lowest 
grade,  were  among  the  highest :  they  were  Ganoids,  or  reptil- 
ian Fishes.  Trilobites,  found  in  the  first  fauna  of  the  Silu- 
rian, are  not  the  lowest  of  Crustaceans.  No  fossil  Snakes 
have  been  found  below  the  Cenozoic,  although  large  Eeptiles 
abounded  in  the  Mesozoic.  Oxen  date  from  the  later  Ter- 
tiary, long  after  the  first  appearance  of  many  higher  Mam- 
mals, as  Tigers,  Dogs,  Monkeys,  etc. 

There  was  upward  progress  in  the  grand  series  of  species, 
as  stated  on  page  250 ;  but  there  was  not  progress  in  all  cases 
from  the  lowest  species  to  the  highest. 

5.  The  earliest  species  of  a  group  were  often  those  of  a  compre- 
hensive type.  —  The  Ganoid  fishes  are  an  example  of  these 
comprehensive  types.     As  stated  on  page  112,  they  were  in- 


254  HISTORICAL  GEOLOGY. 

termediate  in  some  respects  between  Fishes  and  Reptiles; 
they  were  fishes  comprehending  in  their  structure  some  Rep- 
tilian characters,  and  hence  called  comprehensive  types. 

The  earliest  Mammals  were  Marsupials,  or  species  of  Mam- 
mals comprehending  in  their  structure  some  characteristics  of 
oviparous  Vertebrates  (see  page  50),  and,  therefore,  in  certain 
respects  intermediate  between  Mammals  and  Oviparous  Ver- 
tebrates. 

The  vegetation  of  the  coal-era  consisted  largely  of  trees  al- 
lied to  the  Lycopods  or  Ground-pine  of  the  present  day  ;  and 
these,  as  well  as  the  Lycopods,  constitute  a  type  intermediate 
in  some  points  between  Ferns  and  Pines  or  Conifers  (page 
107). 

In  the  Mesozoic  the  most  characteristic  plants  were  Cy- 
cads;  and  these  comprehended  in  their  structure  something 
of  three  distinct  types.  They  are  closely  like  Conifers  in 
structure  and  fruit ;  but  they  are  like  Ferns  in  the  way  the 
leaves  unfold  and  in  some  other  points,  and  like  Palms  in 
their  foliage  (page  162). 

These  comprehensive  types  embraced  in  their  natures  usu- 
ally the  features  of  some  type  that  was  to  appear  in  the  fu- 
ture. Thus,  the  Ganoid  fishes  of  the  Devonian  foreshadowed 
the  type  of  Reptiles,  the  species  under  which  did  not  come 
into  existence  until  long  afterward  in  the  Carboniferous  age. 

6.  Harmony  in  the  life  of  a  period  or  age.  —  Through  the  ex- 
istence of  these  comprehensive  types,  and  also  in  other  ways, 
there  was  always  a  striking  degree  of  harmony  between  the 
species  making  up  the  population  —  or  the  fauna  and  flora 
—  of  each  period  in  the  world's  history. 

Among  the  plants  of  the  Carboniferous  age  there  were  — 
(1)  the  highest  of  the  Cryptogams,  or  Flowerless  plants,  the 
Ferns ;  (2)  the  lowest  of  Phenogams  (Gymnosperms),  or  Flow- 
ering plants,  species  having  only  inconspicuous  and  imperfect 
flowers,  and  hence  almost  flowerless  ;  and  (3)  the  intermediate 
types  of  Lycopods  (Lepidodendrids  and  Sigillarids). 

Again,  in  the  Mesozoic  the  terrestrial  Vertebrate  life  in- 


PROGRESS   OF  LIFE.  255 

eluded  —  (1)  Eeptiles,  which  are  oviparous  species ;  (2)  Birds, 
also  oviparous  species;  (3)  reptilian  Birds,  having  long  tails 
like  the  Eeptiles,  and  in  part,  at  least,  true  teeth,  —  a  compre- 
hensive type ;  (4)  Eeptiles  that  had  the  hollow  leg-bones,  and 
the  biped  locomotion,  of  birds,  with  some  other  bird-like  char- 
acteristics; (5)  semi-oviparous  Mammals,  or  Marsupials,  an 
intermediate  type  between  ordinary  Mammals  and  the  ovip- 
arous Eeptiles  and  Birds. 

7.  Causes  of  the  extinction  of  species  and  tribes.  —  1.  Some 
species  of  plants  and  animals  require  dry  land  for  their  sup- 
port and  growth  ;  some,  fresh- water  marshes  or  lakes  ;  some, 
brackish  water ;  some,  sea-shore  or  shallow  marine  waters ; 
some,  deeper  ocean-waters. 

Hence  (a)  movements  in  the  earth's  crust  submerging  large 
Continental  areas,  or  raising  them  from  the  condition  of  a  sea- 
bottom  to  dry  land,  would  exterminate  life  :  sinking  them 
in  the  ocean,  extinguishing  terrestrial  life ;  raising  them  from 
the  ocean,  extinguishing  marine  life.  In  early  times,  when 
the  Continental  surface  was  in  general  nearly  flat,  a  change  of 
level  of  a  few  hundred  feet,  or  perhaps  of  even  100,  would 
have  been  sufficient  for  a  wide  extermination.  If  a  modern 
coral  island  were  to  be  raised  150  feet,  its  reef-forming  corals 
would  all  be  killed ;  or  if  sunk  in  the  ocean  150  feet,  the 
same  result  would  follow,  —  because  the  species  do  not  grow 
below  a  depth  of  100  feet.  And  if  all  the  coral-reefs  of  the 
Pacific  were  simultaneously  sunk  or  raised  to  the  extent 
stated,  there  would  be  a  total  extinction  of  a  large  number  of 
species. 

(6)  Along  a  sea-coast,  the  bays  and  inlets  sometimes  are 
closed  by  barriers  thrown  up  by  the  sea,  and  hence  become 
fresh,  killing  all  marine  life.  Again,  barriers  are  often  washed 
away  by  the  sea,  and  then  salt  water  enters,  destroying  fresh- 
water life. 

2.  Species  also  endure  a  limited  range  of  temperatures  : 
some  are  confined  thereby  to  the  equatorial  regions  only ; 
some,  to  the  cooler  part  of  the  tropical  zone ;  some,  to  the 


256  HISTORICAL   OEOLOGY. 

warmer  temperate  latitudes  ;  some,  to  the  middle  temperate ; 
some,  to  the  colder  temperate  ;  some,  to  the  frigid  zone  ;  and 
few  species  live  through  two  such  zones.  So  also,  for  the 
same  reason,  they  are  confined  to  specific  ranges  of  height 
above  the  sea-level ;  or  of  depths  below  the  ocean's  surface. 

Hence,  (a)  as  the  earth  has  gradually  cooled  in  its  climates 
from  a  time  of  universal  tropics  to  that  of  the  present  condi- 
tion, the  larger  part  of  those  tribes  or  families  that  were  fitted 
for  the  earlier  condition  of  the  globe  in  the  course  of  time 
became  extinct. 

Again,  (6)  any  temporary  change  of  climate  over  the 
globe  —  from  cold  to  warm  or  warm  to  cold  —  would  have 
exterminated  species.  An  increase  in  the  extent  and  height 
of  Arctic  lands  would  have  increased  the  cold  directly,  be- 
sides shutting  out  from  the  northern  seas  the  warm  cur- 
rents of  the  oceans ;  and  thereby  cold  winds  would  have 
been  sent  south  over  the  continents,  and  cold  oceanic  cur- 
rents south  along  the  borders  of  the  oceans,  or  the  Conti- 
nental seas.  This  cause  is  one  capable  of  carrying  destruc- 
tion over  the  Occident  and  Orient  simultaneously. 

On  the  contrary,  a  diminution  in  the  extent  of  Arctic 
lands,  making  the  higher  regions  open  seas,  and  opening  the 
Arctic  to  the  warm  currents  of  the  oceans,  or  an  increase  in 
the  extent  of  tropical  lands  for  the  sun  to  heat,  would  have 
increased  the  heat  of  the  globe  and  sent  a  warm  climate  far 
north. 

Such  changes  are  destructive  to  living  species.  It  is  sug- 
gested on  page  201  that  the  destruction  of  life  at  the  close 
of  the  Mesozoic  may  have  arisen  from  the  cause  here  ex- 
plained. 

3.  Any  cause  that  in  past  time  led  to  variations  in  species 
tended  to  obliterate  old  characteristics  and  introduce  those 
that  were  new. 

8.  A  parallelism  between  the  progress  in  the  system  of  life  and 
the  development  from  the  embryo  or  young  state  of  a  species.  — 
The  young  gar-pikes  (Ganoids)  of  North  American  waters  have 


PROGRESS   OF  LIFE.  257 

a  vertebrated  tail ;  and  so  it  was  with  the  Gars  of  the  young 
world.  The  young  of  the  higher  Crustaceans,  Shrimps,  Lob- 
sters, and  Crabs,  are  very  similar, —  strangely  similar,  it  might 
be  said  by  one  not  familiar  with  the  generality  of  Nature's 
laws,  —  to  many  Crustaceans  of  the  young  world,  that  is,  of  its 
earliest  age  after  life  began.  Again,  the  young  of  the  higher 
Insects  are  grubs  and  caterpillars ;  and  these  are  related  in 
important  respects  to  Worms,  the  lowest  of  Articulates  and 
the  kind  that  long  preceded  Insects.  This  principle,  announced 
by  Agassiz,  might  be  illustrated  by  examples  from  all  depart- 
ments of  the  animal  kingdom. 

9.  Progress  always  the  gradual  unfolding  of  a  system.  —  Man 
the  culmination  of  that  system.  —  There  were  higher  and  lower 
species  appearing  through  all  the  ages,  but  the  successive  pop- 
ulations were  still,  in  their  general  range,  of  higher  and  higher 
grade  ;  and  thus  the  progress  was  ever  upward.  The  type  or 
plan  of  vegetation,  and  the  four  grand  types  or  plans  of  ani- 
mal life,  the  Eadiate,  Molluscan,  Articulate,  and  Vertebrate, 
were  each  displayed  under  multitudes  of  tribes  and  species, 
rising  in  rank  with  the  progress  of  time,  and  all  under  rela- 
tions so  harmonious  and  so  systematic  in  their  successions 
that  they  seem  like  the  expression  —  in  material  living 
forms  —  of  one  divine  purpose.  A  scheme  carried  forward 
by  infinite  wisdom  should  exhibit,  through  each  step  of  its 
progress,  that  complete  adaptation  to  external  conditions 
which  pervades  the  actual  system  of  Nature,  and  could  result 
in  no  other  than  this  very  system.  Its  progress,  if  by  divine 
power,  should  be,  as  zoological  history  attests,  a  development, 
an  unfolding,  an  evolution. 

With  every  new  fauna  and  flora  in  the  passing  periods, 
there  was  a  fuller  and  higher  exhibition  of  the  kingdoms  of 
life.  Had  progress  ceased  with  the  Eeptilian  age,  the  system 
might  have  been  pronounced  the  scheme  of  an  evil  demon. 
But,  as  time  moved  on,  higher  races  were  introduced;  and 
finally  Man  came  forth,  —  not  in  strength  of  body,  but  in 
the  majesty  of  his  spirit ;  and  then  living  nature  was  full 

Q 


258  HISTORICAL  GEOLOGY. 

of  beneficence.  The  system  of  life,  about  to  disappear  as  a 
thing  of  the  past,  had  its  final  purpose  fulfilled  in  the  crea- 
tion of  a  spiritual  being,  —  one  having  powers  to  search  into 
the  depths  of  nature  and  use  the  wealth  of  the  world  for 
his  physical,  intellectual,  and  moral  advancement, '  that  he 
might  thereby  prepare,  under  divine  aid,  for  the  new  life  in 
the  coming  future. 

Thus,  through  the  creation  of  Man  completing  the  system 
of  life,  all  parts  of  that  system  became  mutually  consistent 
and  full  of  meaning,  and  Time  was  made  to  exhibit  its  true 
relation  to  Eternity. 

10.  The  progress  in  the  system  of  life,  a  progress  in  ceph- 
alization. —  A  frog  in  the  young  state  is  a  tadpole ;  that  is,  has 
a  long  tail  behind,  and  outside  gills  either  side  of  the  head, 
and  it  is  hardly  above  the  lower  fishes  in  grade.  On  passing 
to  the  adult  state,  the  body  is  shortened  in  behind  by  the  loss 
of  the  tail,  the  fish-like  gills  are  dropped  off  from  the  head,  and, 
simultaneously,  the  anterior  or  head  extremity  becomes  vastly 
improved  in  its  structure  and  functions.  This  transfer  of 
forces  anteriorly  marked  in  abbreviation  behind  and  improve- 
ment in  the  rest  of  the  animal,  especially  in  the  organs  of  the 
head,  that  is,  cephalically  (the  Greek  /ce^aXri  meaning  head), 
is  an  example  under  the  principle  of  cepJialization.  There  is 
similar  head  ward  progress  in  all  development  from  the  young 
state,  whatever  the  class  of  animal ;  and  in  Man,  at  the  head 
of  the  system,  many  years  pass  before  the  structure  has  the 
degree  of  cephalization  that  belongs  to  maturity.  In  a  fly, 
the  young,  a  maggot,  is  much  like  a  worm,  the  body  consisting 
of  a  number  of  similar  segments  and  the  head  extremity  little 
superior  to  the  opposite.  But  in  the  adult  fly,  this  extremity 
has  its  well-constructed  head  and  senses,  and  the  posterior  ex- 
tremity, besides  being  reduced  in  relative  size,  aids  no  longer 
in  locomotion ;  the  development  is,  in  a  wonderful  degree,  a 
cephalization  of  the  structure.  Such  examples  of  the  prin- 
ciple of  cephalization  are  afforded  by  every  part  of  the  animal 
kingdom. 


PROGRESS  OF  LIFE.  259 

The  principle  is  exemplified,  also,  in  the  relations  of  the 
inferior  species  of  a  group  to  the  higher.  A  Lobster  and  a 
Crab  (both  Decapod  Crustaceans)  are  essentially  alike  in  fun- 
damental points  of  structure.  The  Lobster  has  a  very  large 
and  powerful  tail  (abdomen),  a  long  and  loosely  compacted 
head,  and  also  large  and  spreading  head-organs ;  while  the 
Crab,  much  the  higher  species,  has  the  tail  reduced  to  a  small, 
feeble  organ,  hid  away  in  a  groove  under  the  thorax,  and,  at 
the  same  time,  the  head  and  the  organs  of  the  senses  and 
mouth  connected  with  it  are  closely  compacted.  Abbrevia- 
tion behind,  and  compacting  and  improvement  in  front,  con- 
nected with  differences  of  grade,  are  here  well  displayed. 

Thus  grade  among  the  species  of  a  group  is  marked  by  dif- 
ferences in  the  degree  of  cephalization  of  the  structure ;  and 
this  is  so  through  all  groups. 

If,  then,  difference  in  grade  among  species  is  manifested 
in  difference  in  cephalization,  and  if  also  the  stages  in  the 
development  of  a  species  mark  progress  in  cephalization,  it  is 
plain  that  the  scheme  of  progress  for  the  animal  kingdom  in- 
volved throughout  progressing  cephalization.  In  geological 
history  there  were  vertebrate-tailed  Ganoids  before  the  non- 
vertebrate-tailed,  tailed  Amphibians  and  Birds  before  the 
tailless,  Worms  before  the  compact  and  highly  cephalized 
Insect,  Shrimps  and  Lobsters  before  Crabs ;  and  so  in  other 
branches  of  the  Animal  Kingdom.  In  Man,  the  last  term  in 
the  series,  cephalization  reached  its  extreme  limit. 

The  system  of  progress  hence  involved  also  changes  in  ani- 
mal structures.  An  animal  with  the  high  senses  of  an  Insect 
could  not  have  the  form  of  a  Worm  ;  or  those  of  a  Crab,  the 
form  of  a  Lobster ;  or  those  of  Man,  the  body  or  head  of  a 
Monkey. 

II  Were  the  intervals  between  species  or  groups  in  the  suc- 
cession, through  past  time,  abrupt,  or  gradual  ?  —  As  Geology  is 
the  history  of  the  progress  of  the  earth  and  its  life,  the  science 
is  naturally  looked  to  for  a  decision  of  the  great  question, 
Whether,  in  the  succession  of  species  during  past  time,  there 


260  HISTORICAL  GEOLOGY. 

were  gradual  transitions  between  them  or  not.  Its  testimony 
could  not,  however,  be  decisive,  unless  the  record,  in  some 
parts  at  least,  were  a  nearly  unbroken  one. 

There  is  abundant  evidence  that,  to  a  large  extent,  it  is,  as 
has  been  claimed,  a  very  broken  record.  For  example  :  there 
is  not,  on  the  eastern  half  of  North  America,  the  Atlantic  bor- 
der included,  a  species  of  the  marine  Molluscan  or  Eadiate 
life  of  that  border  during  the  long  Triassic  and  Jurassic  periods. 
That  there  were  abundant  species  in  the  seas  is  evident  from 
the  rocks  of  these  eras  in  Europe.  Coast  deposits  on  the 
Atlantic  must  have  been  made ;  but  they  are  out  of  reach  be- 
neath the  ocean's  waters.  Again,  two  jaw-bones  of  one  species 
of  Marsupial  Mammal  are  all  the  relics  that  have  been  found 
of  these  animals  in  rocks  of  the  North  American  Triassic, 
Jurassic,  and  Cretaceous  periods,  or  the  whole  of  Mesozoic 
time ;  and  yet,  if  there  were  one  species  in  the  Triassic,  and 
two  individuals,  there  were  probably  a  large  number  of  species, 
and  multitudes  must  have  lived  and  died  through  the  Meso- 
zoic era.  In  Europe,  one  single  specimen  of  a  bird  has  been 
found  in  Jurassic  rocks,  out  of  the  myriads  of  individuals  and 
the  great  numbers  of  species  that  must  then  have  lived.  Only 
a  very  few  kinds  of  plants  have  been  found  in  the  Mesozoic 
formations  of  North  America,  and  yet,  the  continent  must 
have  been  buried  in  foliage  through  all  the  successive  periods 
after  the  Carboniferous  age. 

It  has  to  be  admitted  that  we  know  very  little  about  the 
past  terrestrial  life  of  the  globe,  and  also  that  there  are  some 
great  breaks  in  the  succession  of  marine  life.  Moreover, 
breaks,  as  geological  history  shows,  may  exist  where  the  rocks 
follow  one  another  consecutively  without  any  apparent  inter- 
ruption. 

Now,  in  the  succession  of  species  made  known  by  geology, 
the  transitions  connecting  species  or  groups  are  abrupt,  and 
not  gradual.  Some  of  the  links  between  genera  have  been 
partially  filled  out  by  recent  discoveries,  as,  for  instance,  that 
between  the  modern  Horse  and  the  Tapir-like  Mammals  of 


PROGRESS  OF  LIFE.  261 

the  Eocene  (page  213),  and  that  between  the  Elephant  and 
the  Mastodon,  etc. ;  but  still  the  species  and  genera  of  Horses 
stand  apart.  In  the  long  geological  succession  of  groups  there 
are  even  fewer  examples  of  blendings  than  occur  in  existing 
life. 

Yet  it  has  to  be  admitted  that  the  above  facts  with  regard 
to  the  breaks  in  the  series  of  rocks  weaken  greatly  this  evi- 
dence against  gradual  transitions.  And  its  force  is  further 
lessened  by  the  fact  that  geological  exploration  has  not  ex- 
tended to  all  parts  of  the  world,  or  exhausted  discovery  in  the 
portions  that  have  been  investigated.  This  is  especially 
true  of  the  terrestrial  life  of  the  globe ;  but  not  so  strongly 
with  regard  to  the  marine  life,  particularly  the  Paleozoic  part, 
since  the  rocks  of  the  earlier  ages  are  mainly  of  marine  origin, 
and  abound  in  fossils. 

There  are  still  some  breaks  that  are  most  remarkable,  what- 
ever allowance  be  made  for  imperfection  of  records.  (1.)  Tri- 
lobites  and  Brachiopods  come  abruptly  into  geological  history 
with  no  recognizable  traces  of  their  antecedents.  (2.)  Fishes, 
the  first  of  Vertebrates,  appear  in  the  later  Silurian,  with  no 
species  between  them  and  the  Invertebrates  as  their  precursors. 
(3.)  The  leaves  of  Angiosperms  (or  trees  of  modern  tribes  re- 
lated to  the  Willow,  Elm,  Magnolia)  and  also  the  Palms,  are 
found  fossil  in  the  Cretaceous  rocks  of  the  continents,  and  none 
whatever  as  yet  in  the  Jurassic. 

The  Triassic  rocks  have  afforded  bones  of  the  first  Mam- 
mals, —  Marsupial  Mammals ;  but  nothing  with  regard  to  the 
line  of  predecessors  connecting  them  with  inferior  oviparous 
species.  The  Tertiary  rocks  of  all  the  continents  abound,  in 
many  places,  in  remains  of  true  Mammals.  Yet  not  a  trace 
of  one  has  been  found  in  the  Cretaceous  strata ;  and  this  is 
true  even  in  the  Eocky  Mountain  region,  where  the  strata  are 
mostly  of  shallow- water  origin,  and  partly  of  fresh- water  for- 
mation. These  last  are  examples,  it  is  true,  from  terrestrial 
species.  But  the  very  long  blank  antecedent  to  the  Marsu- 
pials and  to  the  true  Mammals  may  well  suggest  the  pro- 


262  HISTORICAL  GEOLOGY. 

priety  of  making  further  search  before  assuming  that  in  the 
gradation  upward  there  were  no  greater  interruptions  than  are 
illustrated  by  the  variations  among  existing  Mammals. 

In  the  case  of  Man,  the  abruptness  of  transition  is  still 
more  wonderful.  The  Man-ape,  nearest  in  structure  to  Man, 
has  a  cranium  of  but  34  cubic  inches  in  capacity,  or  half  that 
of  the  lowest  of  existing  Man,  and  no  link  between  has  been 
found.  No  human  remains  that  the  past  fifteen  years  of 
active  search  have  brought  to  light  afford  evidence  of  the  ex- 
istence of  a  race  less  perfectly  erect  than  existing  Man,  or 
nearer  to  the  Man-ape  in  essential  characteristics.  The  Man- 
apes  of  the  present  day,  the  Gorilla,  Chimpanzee,  and  Orang- 
Utan,  are  the  terminations  of  lines  of  succession  that  reached 
up  to  them.  But,  as  to  the  line  supposed  to  end  in  Man,  not 
the  first  link  has  been  found.  Thus  geological  discovery 
leaves  Man  alone  at  the  head  of  the  system  of  life,  far  re- 
moved from  his  nearest  allies  among  the  brute  races. 

12.  Origin  of  Species.  —  Such  is  the  direct  evidence  from 
Geology  as  to  the  transitions  between  species.  The  other 
considerations,  derived  from  Geology,  that  have  been  regarde'd 
as  bearing  on  the  question  of  the  origin  of  species,  are  — 

1.  That  the  system  of  life  exhibits  so  perfect  harmony, 
and  so  complete  oneness  of  law  in  its  several  lines  and  suc- 
cessions, that  it  may  be  truly  called  a  system  of  development 
or  evolution,  whatever  the  method  by  which  it  was  carried 
forward  (page  257). 

2.  That  since  the  physical  progress  of  the  globe  was  under 
the  action  of  natural  law,  so  the  same  may  naturally  have 
been  true  of  its  organic  progress. 

3.  That,  as  regards  geological  history,  time  is  long, 

These  arguments  in  themselves  are  an  insufficient  basis  for 
a  settlement  of  the  great  question. 

Science  derives  other  evidences  from  the  study  of  living 
plants  and  animals ;  but  this  is  not  the  place  for  their  presen- 
tation. Still  other  arguments  come  from  a  priori,  abstract,  or 
metaphysical  considerations,  and  these  too  would  be  here  out 
of  place. 


PROGRESS  OF  LIFE.  263 

The  biblical  student  finds,  in  the  first  chapter  of  Genesis, 
positive  statements  with  regard  to  the  creation  of  living  be- 
ings. But  these  statements  are  often  misunderstood ;  for 
they  really  leave  the  question  as  to  the  operation  of  natural 
causes  for  the  most  part  an  open  one,  —  as  asserted  by  Augus- 
tine, among  the  Fathers  of  the  Church,  and  by  some  biblical 
interpreters  of  the  present  day;  for  it  says  that  there  were 
but  four  fiats  for  the  whole ;  or  but  two,  excluding  the  first 
for  the  beginning  of  life,  and  the  last  for  the  creation  of  Man. 
And  it  plainly  implies  that,  after  the  fiats,  that  is,  through 
these  expressions  of  the  Divine  Will,  the  new  developments 
went  forward  successively  to  the  completion  of  the  grand 
system. 

In  view  of  the  whole  subject,  the  following  appear  to  be 
the  conclusions  most  likely  to  be  sustained  by  further  re- 
search. 

1.  The  evolution  of  the  system  of  life  went  forward  through 
the  derivation  of  species  from  species,  according  to  natural 
methods  not  yet  clearly  understood,  and  with  few  occasions 
for  supernatural  intervention. 

2.  The  method  of  evolution  admitted  of  abrupt  transitions 
between  species ;  as  has  been  argued  from  the  abrupt  transi- 
tions that  occur  in  the  development  of  animals  that  undergo 
metamorphosis,  and  the  successive  stages  in  the  growth  of 
many  others. 

3.  External  agencies  or  conditions,  while  capable  of  pro- 
ducing modifications  of  structure,  have  had  no  more  power 
toward  determining  the  directions  of  progress  in  the  evolution, 
than  they  now  have  in  determining  the  course  of  progress  in 
development  from  a  living  germ. 

4.  For  the  development  of  Man,  gifted  with  high  reason 
and  will,  and  thus  made  a  power  above  Nature,  there  was 
required,  as  Wallace  has  urged,  the  special  act  of  a  Being 
above  Nature,  wiiose  supreme  will  is  not  only  the  source  of 
natural  law,  but  the  working  force  of  Nature  herself. 


PART  IV. 

DYNAMICAL    GEOLOGY. 


DYNAMICAL  GEOLOGY  treats  of  the  causes  or  origin  of 
events  in  Geological  history,  —  that  is,  of  the  origin  of  rocks, 
of  disturbances  of  the  earth's  strata  and  the  accompanying 
effects,  of  valleys,  of  mountains,  of  continents,  and  of  the 
changes  in  the  earth's  features,  climates,  and  living  species. 

The  agencies  of  most  importance,  next  to  the  universal 
power  of  Gravitation,  are  Life,  the  Atmosphere,  Water,  Heat, 
and  Cohesive  and  Chemical  attraction. 

The  following  are  the  subdivisions  of  the  subject  here 
adopted  :  1.  Life ;  2.  The  Atmosphere ;  3.  Water ;  4.  Heat, 
—  the  mechanical  effects  of  the  Atmosphere,  Water,  and 
Heat  being  considered  under  these  heads ;  5.  Movements  in 
the  earth's  crust,  and  their  consequences,  including  the  fold- 
ing and  uplifting  of  strata,  the  production  of  earthquakes,  and 
the  origin  of  mountains  and  of  the  earth's  general  features. 
Chemical  Geology,  which  treats  of  the  chemical  operations 
connected  with  the  origin  of  rocks,  constitutes  another  divi- 
sion of  the  subject,  but  is  not  here  taken  up. 

I.  — LIFE. 

Life  has  done  much  geological  work  by  contributing  mate- 
rial for  the  making  of  rocks.  Nearly  all  the  limestones  of 
the  globe,  all  the  coal,  and  some  siliceous  beds,  besides  por- 


PEAT-FORMATIONS.  265 

tions  of  rocks  of  other  kinds,  have  been  formed  out  of  the 
stony  relics  of  living  species. 

Through  simple  growth  and  the  power  of  secretion,  Verte- 
brates form  a  bony  skeleton ;  Mollusks  make  shells,  which  are 
calcareous,  or  nearly  of  the  composition  of  common  lime- 
stone; Polyps  make  Corals,  also  calcareous;  Crinoids  make 
stems  and  flower-shaped  skeletons  that  are  calcareous;  and 
the  Polyps  and  Crinoids,  although  as  really  animal  as  any 
quadruped,  are  yet  so  low  in  organization  that  nine  tenths  of 
the  bulk  of  the  animal  are  often  stony  (calcareous),  and  still 
the  functions  of  life  are  perfectly  carried  on. 

There  are  various  kinds,  also,  of  microscopic  species 
which  contribute  to  the  material  of  rocks.  The  Rhizopods 
among  animals  (page  50)  make  calcareous  shells,  each 
containing  one  or  many  minute  cells ;  the  Diatoms  among 
microscopic  plants  (page  61)  make  siliceous  shells ;  the 
Polycystines  (page  59)  among  microscopic  animals  make 
siliceous  shells. 

Plants  also  make  beds  of  coal  and  peat  out  of  accumula- 
tions of  leaves  and  stems,  as  already  in  part  explained  on 
page  133. 

In  further  illustration  of  this  subject,  three  examples  of 
rock-making  are  here  described  :  1.  Peat-formations ;  2.  Beds 
of  microscopic  organisms ;  3.  Coral-reefs. 

1.  Peat-formations. 

Peat  is  an  accumulation  of  half-decomposed  vegetable 
matter  formed  in  wet  or  swampy  places.  In  temperate 
climates  it  is  due  mainly  to  the  growth  of  mosses  of  the 
genus  Sphagnum.  These  mosses  form  a  loose  turf ;  and,  as 
they  have  the  property  of  dying  at  the  extremities  of  the 
roots  while  increasing  above,  they  may  gradually  form  a  bed 
of  great  thickness.  The  roots  and  leaves  of  other  plants,  or 
their  branches  and  stumps,  and  any  other  vegetation  present, 
may  contribute  to  the  accumulating  bed.  The  carcasses  and 
12 


266  DYNAMICAL   GEOLOGY. 

excrements  of  dead  animals  at  times  become  included.  Dust 
may  also  be  blown  over  the  marsh  by  the  winds. 

In  wet  parts  of  Alpine  regions  there  are  various  flowering 
plants  which  grow  in  the  form  of  a  close  turf,  and  give  rise 
to  beds  of  peat  like  the  moss.  In  Fuegia,  although  not  south 
of  the  parallel  of  56°,  there  are  large  marshes  of  such  Alpine 
plants,  the  mean  temperature  being  about  40°  F. 

The  dead  and  wet  vegetable  mass  slowly  undergoes  a 
change,  becoming  an  imperfect  coal,  of  a  brownish-black 
color,  loose  in  texture,  and  often  friable,  although  commonly 
penetrated  with  rootlets.  In  the  change  the  woody  fibre  loses 
a  part  of  its  gases ;  but,  unlike  coal,  it  still  contains  usually  25 
to  33  per  cent  of  oxygen.  Occasionally  it  is  nearly  a  true  coal. 

Peat-beds  cover  large  surfaces  of  some  countries,  and  occa- 
sionally have  a  thickness  of  forty  feet.  One  tenth  of  Ireland 
is  covered  by  them ;  and  one  of  the  "  mosses  "  of  the  Shannon 
is  stated  to  be  fifty  miles  long  and  two  or  three  broad.  A 
marsh  near  the  mouth  of  the  Loire  is  described  by  Blavier  as 
more  than  fifty  leagues  in  circumference.  Over  many  parts 
of  New  England  and  other  portions  of  North  America  there 
are  extensive  beds.  The  amount  in  Massachusetts  alone  has 
been  estimated  to  exceed  120,000,000  of  cords.  Many  of  the 
marshes  were  originally  ponds  or  shallow  lakes,  and  gradually 
became  swamps  as  the  water,  from  some  cause,  diminished  in 
depth. 

Peat  is  often  underlaid  by  a  bed  of  whitish  shell  marl, 
consisting  of  fresh- water  shells  —  mostly  species  of  Lyn- 
ncea,  Physa,  and  Planorbis  —  which  were  living  in  the  lake. 
There  are  often  also  beds  of  a  white  chalky  material  con- 
sisting of  the  siliceous  shields  of  Diatoms. 

Peat  is  used  for  fuel,  and  also  as  a  fertilizer.  Muck  is 
another  name  of  peat,  and  is  used  especially  when  the  ma- 
terial is  employed  as  a  manure;  but  it  includes  also  im- 
pure varieties  not  fit  for  burning,  being  applied  to  any  black 
swamp-earth  consisting  largely  of  decomposed  vegetable 
matter. 


BEDS  OF  MICROSCOPIC  ORGANISMS.  267 

Peat-beds  sometimes  contain  standing  trees,  and  entire 
skeletons  of  animals  that  had  sunk  in  the  swamp.  The  peat- 
waters  have  often  an  antiseptic  power,  and  flesh  is  sometimes 
changed  by  the  burial  into  adipocere. 


2.  Beds  of  Microscopic  Organisms. 

Microscopic  life  abounds  in  almost  all  waters,  especially 
over  muddy  bottoms,  —  as  in  lakes,  rivers,  marshes,  salt-water 
swamps,  harbors,  bays,  the  shallow  borders  of  the  ocean,  and 
also  the  deep  ocean.  Part  of  the  species  make  no  stony 
secretions,  but  much  the  larger  part  form  calcareous  or  sili- 
ceous shells.  Although  these  shells  are,  with  few  exceptions, 
exceedingly  minute,  the  most  part  wholly  invisible  unless 
highly  magnified,  they  are  in  so  vast  numbers  in  many  places, 
and  multiply  so  rapidly,  that  they  form  in  time  thick  beds. 
A  square  yard  covered  with  these  microscopic  species  will 
increase  upward  not  only  as  fast  as  a  square  yard  of  an 
oyster-bank,  but  much  more  rapidly,  because  of  their  extreme 
simplicity  of  structure,  their  rapid  reproduction,  and  the  fact 
that  nearly  the  whole  bulk  of  each  one  is  in  stony  material. 

The  calcareous  species,  or  Ehizopods,  abound  in  the  shallower 
waters  along  the  borders  of  the  ocean,  and  also  over  its  bottom 
where  thousands  of  feet  deep.  Over  what  is  called  the  Tele- 
graphic plateau,  between  Ireland  and  Newfoundland,  they 
appear  to  make  a  nearly  continuous  bed  for  a  thousand  miles 
or  more  in  breadth,  and  perhaps  more  than  this  from  north  to 
south.  The  thickness  of  the  great  chalk-formation  there  in 
progress,  out  of  these  minute  shells,  is  of  course  unknown. 
The  genera  of  shallow  water  are  in  part  different  from  those 
of  the  deep  sea.  There  are  also  among  plants,  the  microscopic 
Coccoliths  (page  61)  which  abound  over  the  ocean's  bed. 

The  siliceous  species  are  either  Diatoms  or  Polycystines. 
They  occur  both  in  shallow  and  deep  waters,  like  the  Ehizo- 
pods.  The  Diatoms  .are  found  in  cold  as  well  as  warm  seas, 
and  in  fresh  waters  as  well  as  marine.  Over  the  bottoms  of 


268  DYNAMICAL  GEOLOGY. 

shallow  lakes  they  make  thick  beds,  just  as  the  Ehizopods 
do  in  the  ocean ;  and  many  of  the  peat-beds  rest  on  a  thick 
layer  of  Diatoms  made  from  species  that  were  living  in  the 
lake  that  afterwards  became  the  peat-growing  swamp.  The 
siliceous  spicules  of  sponges  contribute  to  the  marine  deposits, 
and  somewhat  also  to  those  of  fresh  water. 

The  rock  made  of  Ehizopod  shells  is  exemplified  in  chalk, 
—  a  soft,  white  or  whitish,  limestone.  That  consisting  of 
Diatoms  often  looks  like  a  very  fine  whitish  earth ;  but  it  is 
sometimes  compacted  into  a  nearly  solid  mass,  and  sometimes 
into  an  imperfect  slate.  Flint  is  made  mainly  of  Diatoms 
and  of  the  spicules  of  sponges. 

There  are  examples  of  beds  formed  by  the  simple  growth 
and  multiplication  of  living  species.  The  shells  are  in  size 
like  the  grains  of  a  fine  powder ;  and  it  is  only  necessary  that 
they  be  consolidated  as  they  lie,  in  order  that  a  compact  rock 
may  be  made  out  of  the  accumulation. 


3.  Coral-reefs. 

In  tropical  regions  corals  grow  in  vast  plantations  about 
most  oceanic  islands  and  along  the  shores  of  continents.  The 
greatest  depth  at  which  the  reef-making  species  live  is  about 
100  feet;  and  from  this  depth  to  sometimes  a  foot  above  low- 
tide  level  they  flourish  well.  The  patches  or  groves  of  coral 
are  usually  distributed  among  larger  areas  of  coral  sand,  like 
small  groves  of  trees  or  shrubbery  in  some  sandy  plains. 

The  corals  have  much  resemblance  to  vegetation  in  their 
forms  and  their  modes  of  growth ;  and  the  animals  are  so  like 
flowers  in  shape  and  bright  colors  that  they  are  often  called 
flower-animals  (page  57).  Along  with  the  corals  there  are 
also  great  numbers  of  Shells,  besides  Crabs,  Echini,  and  other 
kinds  of  marine  life. 

The  coral  plantations  are  swept  by  the  waves,  and  with 
great  force  when  the  seas  are  driven  by  storms.  The  corals 
are  thus  frequently  broken,  and  the  fragments  washed  about 


CORAL-REEFS.  239 

until  they  are  either  worn  to  sand  by  the  friction  of  piece 
upon  piece,  or  become  buried  in  the  holes  among  the 
growing  corals,  or  are  washed  up  on  the  beach.  Corals  are 
not  injured  by  mere  breaking,  any  more  than  is  vegetation  by 
the  clipping  of  a  branch ;  and  those  that  are  not  torn  up  from 
the  very  base  and  reduced  to  fragments  continue  to  grow. 

The  fragments  and  sand  made  by  the  waves,  and  by  the 
same  means  strewed  over  the  bottom,  along  with  the  shells 
also  of  Mollusks,  commence  the  formation  of  a  bed  of  coral- 
rock,  —  literally  a  bed  of  limestone,  for  the  coral  and  shells 
have  the  composition  of  limestone,  and  consolidation  goes  on 
simultaneously.  As  the  corals  continue  growing  over  this 
bed,  fragments  and  sand  are  constantly  forming,  and  the  bed 
of  limestone  thus  increases  in  thickness.  In  this  manner  it 
goes  on  increasing  until  it  reaches '  the  level  of  low  tide  ;  be- 
yond this  it  rises  but  little,  because  corals  cannot  grow  where 
they  are  liable  to  be  left  for  a  day  wholly  out  of  water ;  and 
the  waves  have  too  great  force  at  this  level  to  allow  of  their 
holding  their  places,  if  they  were  able  to  stand  the  hot  and 
drying  sun.  The  bed  of  calcareous  rock  thus  produced  is  a 
coral-reef. 

Since  reef-corals  grow  to  a  depth  of  only  100  feet,  the 
thickness  of  the  reef  cannot  much  exceed  100  feet  if  the 
sea-bottom  remains  at  a  constant  level,  except  where  there 
are  oceanic  currents  to  transport  to  greater  depths  the  sand 
that  is  made.  But  should  the  reef-region  be  slowly  sinking 
at  a  rate  not  faster  than  the  corals  can  grow  and  make  the 
reef  rise,  then  almost  any  thickness  may  be  attained.  From 
observations  about  the  coral  regions  of  the  Pacific,  it  is  sup- 
posed that  some  of  the  reefs  have  acquired  a  thickness  of 
two  or  three  thousand  feet  or  more,  during  such  a  slow  sub- 
sidence. 

The  coral  formations  of  the  Pacific  are  sometimes  broad 
reefs  around  hilly  or  mountainous  islands,  as  shown  in  the 
annexed  sketch.  To  the  left,  in  the  sketch,  there  is  an  inner 
reef  and  an  outer  reef,  separated  by  a  channel  of  water,  the 


270 


DYNAMICAL  GEOLOGY. 


inner  of  which  (/)  is  called  a  fringing  reef,  and  the  outer 
(6)  a  barrier  reef.     They   are   united   in   one   beneath   the 


View  of  a  high  island,  bordered  by  coral-reefs. 

water.  At  intervals  there  are  usually  openings  through  the 
barrier  reef,  as  at  h  h,  which  are  entrances  to  harbors.  The 
channels  are  sometimes  deep  enough  for  ships  to  pass  from 
harbor  to  harbor. 

Many  coral-reefs  stand  alone  in  the  ocean,  far  from  any 
other  lands  (Fig.  382).     These   are  called  coral  islands,  or 

Fig.  383. 


Coral  island,  or  atoll 

atolls.      They  usually  consist  of  a  narrow  reef  encircling  a 

salt-water  lake.  The  lake  is  but  a  patch  of  ocean  enclosed  by 
the  reef,  with  its  groves  of  palms  and  other 
tropical  plants.  When  there  are  deep  open- 
ings through  the  reef,  ships  may  enter  the 
lake,  or  lagoon,  as  it  is  usually  called,  and. 
find  excellent  anchorage.  The  annexed  fig- 
ure (Fig.  383)  is  a  map  of  one  of  the  atolls 
of  the  Gilbert  (or  Kingsmill)  Islands  in  the 
Pacific.  The  reef  on  one  side  —  the  wind- 
ward—  is  wooded  throughout;  but  on  the 
other  it  has  only  a  few  wooded  islets,  the 

rest  being  bare  and  partly  washed  by  the  tides.     At  e  there 

is  an  opening  to  the  lagoon. 


Apia,  of  the  Gilbert 
group. 


CORAL-REEFS.  271 

The  Paumotu  Archipelago,  just  northeast  of  the  Society 
Islands,  contains  between  70  and  80  coral  islands ;  the  Caro- 
lines, with  the  Kadack,  Ealick,  and  Gilbert  groups  on  the  east 
and  southeast,  as  many  more ;  and  others  are  scattered  over 
the  intervening  ocean.  Most  of  the  high  islands  between 
the  parallels  of  28°  north  and  south  of  the  equator,  and  also 
the  borders  of  the  continents,  have  a  fringe  of  coral-reefs, 
unless  (1)  the  waters  adjoining  the  coasts  are  too  deep,  or 
(2)  the  bottom  is  too  muddy,  or  (3)  rivers  pour  in  fresh 
waters,  these  being  injurious  to  corals,  or  (4)  cold  oceanic 
currents  sweep  along  the  coasts.  Corals  are  limited  by 
the  parallel  of  28°,  because  they  will  not  nourish  where 
the  mean  temperature  of  the  coldest  winter  month  is  below 
68°  F. 

The  limestone  beds  made  from  corals  and  shells  are  not 
a  result  of  growth  alone,  as  in  the  case  of  the  deposits 
formed  from  microscopic  organisms,  but  of  growth  in  con- 
nection with  the  breaking  and  wearing  action  of  the  ocean's  waves 
and  currents.  Corals  and  shells,  unaided,  could  make  only  an 
open  mass  full  of  large  holes,  and  not  a  solid  rock.  There 
must  be  sand  or  fine  fragments  at  hand,  such  as  the  waters 
can  and  do  constantly  make  in  such  regions,  in  order  to  fill 
up  the  spaces  or  interstices  between  the  corals  or  shells.  If 
there  is  clayey  or  ordinary  siliceous  sand  at  hand,  this  will 
suffice,  but  it  will  not  make  a  pure  limestone  ;  in  order  to 
have  the  rock  a  true  limestone,  the  shells  and  corals  must 
be  the  source  of  the  sand  or  fine  fragments,  for  these  alone 
yield  the  needed  calcareous  material  and  cement.  The 
limestone  made  in  this  way  by  the  help  of  the  waves  may 
be,  and  often  is,  as  fine  grained  as  a  piece  of  flint  or  any  ordi- 
nary limestone,  it  having  been  formed,  in  such  a  case,  of  the 
finest  coral  sand  or  mud.  In  other  cases,  it  contains  some 
imbedded  fragments  in  the  solid  bed ;  in  others,  it  is  a  coral 
conglomerate ;  and,  over  still  other  large  areas,  it  is  a  mass 
of  standing  corals  with  the  interstices  filled  in  solid  with  the 
sand  and  fragments. 


272  DYNAMICAL   GEOLOGY. 

Along  the  shores,  above  low  tide,  the  sands  are  agglutinated 
into  a  beach  sand-rock,  and  the  beds  have  the  slope  of  the 
beach,  or  5°  to  8°.  The  waters  contain  lime  (as  bicarbonate) 
in  solution ;  and  as  the  sands,  wet  at  high  tide,  dry  again 
when  the  tide  is  out,  this  cement  is  deposited  between  the 
grains,  and  so  consolidation  goes  forward.  The  calcareous 
cement  coats  the  grains  with  carbonate  of  lime ;  and  either 
in  this  way,  or  by  its  own  concretionary  tendencies,  the  rock 
sometimes  becomes  an  oolyte,  —  that  is,  a  limestone  made 
up  of  minute  rounded  grains,  with  each  grain  concretionary 
in  structure. 

The  pages  on  the  results  of  microscopic  life  contain  an 
explanation  of  one  method  by  which  the  ancient  limestones 
of  the  globe  have  been  made.  The  process  of  limestone- 
making  now  going  on  through  the  agency  of  coral  animals 
illustrates  another  method,  and  far  the  most  common.  The 
beds,  in  the  case  of  these  limestones,  are  a  result  of  the  slow 
growth  of  living  corals,  crinoids,  shells,  and  the  like,  and  the 
gradual  wearing  of  the  calcareous  remains  more  or  less  com- 
pletely to  mud,  sand,  and  pebbles,  preparatory  for  consolida- 
tion. 

The  extent  of  some  of  the  modern  reefs  matches  nearly 
that  of  the  largest  Paleozoic  reefs.  On  the  north  of  the  Fee- 
jee  Islands  the  reef-grounds  are  5  to  15  miles  in  width.  In 
New  Caledonia  they  extend  150  miles  north  of  the  island  and 
50  miles  south,  making  a  total  length  of  400  miles.  Along 
Northeastern  Australia  they  stretch  on,  although  with  many 
interruptions,  for  1,000  miles.  The  modern  reef-grounds,  al- 
though often  of  great  length,  are,  however,  narrow,  unlike 
those  of  the  early  geological  ages.  But  this  difference  arises 
from  the  fact  that  the  regions  giving  the  requisite  depth  for 
abundant  Coral  and  Molluscan  life  are  now  of  narrow  limits, 
being  confined  to  the  borders  of  the  continents,  whereas  in 
ancient  time  the  continents  were  to  a  large  extent  submerged 
at  shallow  depths  and  afforded  the  conditions  requisite  for 
immense  Coral,  Crinoidal,  and  Molluscan  plantations. 


THE  ATMOSPHERE.  273 

II.  —  THE  ATMOSPHERE. 

The  following  are  some  of  the  mechanical  effects  connected 
with  the  movements  of  the  atmosphere. 

L  Destructive  effects  from  the  transportation  of  sand,  dust,  etc. 
—  The  streets  of  most  cities,  as  well  as  the  roads  of  the  coun- 
try, in  a  dry  summer  day,  afford  examples  of  the  drift  of  dust 
by  the  winds.  The  dust  is  borne  most  abundantly  in  the  di- 
rection of  the  prevalent  winds,  and  may  in  the  course  of  time 
make  deep  beds.  The  dust  that  finds  its  way  through  the 
windows  into  a  neglected  room  indicates  what  may  be  done 
in  the  progress  of  centuries  where  circumstances  are  more 
favorable. 

The  moving  sands  of  a  desert  or  sea-coast  are  the  more 
important  examples  of  this  kind  of  action. 

On  sea-shores,  where  there  is  a  sea-beach,  the  loose  sands 
composing  it  are  driven  inland  by  the  winds  into  parallel 
ridges  higher  than  the  beach,  forming  drift-sand  hills.  They 
are  grouped  somewhat  irregularly,  owing  to  the  course  of  the 
wind  among  them,  and  also  to  little  inequalities  of  compact- 
ness or  to  protection  from  vegetation.  They  form  especially 
(1)  where  the  sand  is  almost  purely  siliceous,  and  therefore 
not  at  all  adhesive  even  when  wet,  and  not  good  for  giving 
root  to  grasses ;  and  (2)  on  windward  coasts.  They  are  com- 
mon on  the  windward  side,  and  especially  the  projecting 
points,  even  those  of  a  coral  island,  but  never  occur  on  the 
leeward  side,  unless  this  side  is  the  windward  during  some 
portion  of  the  year.  On  the  north  side  of  Oahu,  one  of  the 
Sandwich  Islands,  they  are  30  feet  high,  and  made  of  coral 
sand.  Some  of  them,  which  stand  still  higher  (owing  to  an 
elevation  of  the  island),  have  been  solidified,  and  they  show, 
where  cut  through,  that  they  consist  of  thin  layers  lapping 
over  one  another ;  and  they  evince  also,  by  the  abrupt  changes 
of  direction  in  the  layers  (see  Fig.  17  /  page  32),  that  the 
growing  hill  was  often  cut  partly  down  or  through  by  storms, 
and  was  again  and  again  completed  after  such  disasters. 

12*  B 


274  DYNAMICAL   GEOLOGY. 

This  style  of  lamination  and  irregularity  is  characteristic 
of  the  drift-sand  hills  of  all  coasts.  On  the  southern  shore 
of  Long  Island  there  are  series  of  sand-hills  of  the  kind  de- 
scribed, extending  along  for  100  miles,  and  5  to  30  feet  high. 
They  are  partially  anchored  by  straggling  tufts  of  grass.  The 
coast  of  New  Jersey  down  to  the  Chesapeake  is  similarly 
fronted  by  sand-hills.  In  Norfolk,  England,  between  Hun- 
stanton  and  Wey bourne,  the  sand-hills  are  50  to  60  feet 
high. 

2.  Additions  to  land  by  means  of  drift-sands,  —  The  drift-sand 
hills  are  a  means  of  recovering  lands  from  the  sea.     The  ap- 
pearance of  a  bank  at  the  water's  surface  off  an  estuary  at  the 
mouth  of  a  stream  is  followed  by  the  formation  of  a  beach, 
and  then  the  raising  of  hills  of  sand  by  the  winds,  which  en- 
large till  they  sometimes  close  up  the  estuary,  exclude  the 
tides,  and  thus  aid  in  the  recovery  of  the  land  by  the  deposi- 
tions of  river-detritus.   Lyell  observes  that  at  Yarmouth,  Eng- 
land, thousands  of  acres  of  cultivated  land  have  thus  been 
gained  from  a  former  estuary.     In  all  such  results  the  action 
of  the  waves  in  first  forming  the  beach  is  a  very  important 
part  of  the  whole. 

3.  Destructive   effects  of  drift-sands.  —  Dunes.  —  Dunes   are 
regions  of  loose  drift-sand  near  the  sea.     In  Norfolk,  England, 
between  Hunstanton  and  Weybourne,  the  drift-sands  have 
travelled  inland  with  great  destructive  effects,  burying  farms 
and  houses.     They  reach,  however,  but  a  few  miles  from  the 
coast-line,  and  were  it  not  that  the  sea-shore  itself  is  being 
undermined  by  the  waves,  and  is  thus  moving  landward,  the 
effects  would  soon  reach  their  limit.     Dunes  and  drift-heaps 
occur  on  a  grand  scale  also  on  the  Great  Lakes. 

In  the  desert  latitudes,  drift-sands  are  more  extended  in 
their  effects. 

4.  Sand-scratches.  —  The  sands  carried  by  the  winds,  when 
passing  over  rocks,  sometimes  wear  them  smooth,  or  cover 
the  surface  with  scratches  and  furrows,  as  observed  by  W. 
P.  Blake  on  granite  rocks  at  the  Pass  of  San  Bernardino  in 


WATER.  275 

California.  Even  quartz  was  polished,  and  garnets  were  left 
projecting  upon  pedicels  of  feldspar.  Limestone  was  so  much 
worn  as  to  look  as  if  the  surface  had  been  removed  by  solu- 
tion. Similar  effects  have  been  observed  by  Winchell  in  the 
Grand  Traverse  region,  Michigan.  Glass  in  the  windows  of 
houses  on  Cape  Cod  sometimes  has  holes  worn  through  it  by 
the  same  means.  The  hint  from  nature  has  led  to  the  use  of 
sand,  driven  by  a  blast  with  or  without  steam,  for  cutting 
and  engraving  glass,  and  even  for  cutting  and  carving  granite 
and  other  hard  rocks. 

III.— WATER. 

The  subject  of  Water  is  here  considered  under  the  follow- 
ing heads : — 

1.  FRESH  WATERS  ;   including  especially  Eivers   and   the 
smaller  Lakes,  and  also  subterranean  as  well  as  superficial 
waters. 

2.  The  OCEAN  ;  including,  along  with  the  Ocean,  the  larger 
Lakes,  whether  salt  or  fresh. 

3.  FROZEN  WATERS,  or  Glaciers,  and  Icebergs. 

1.  Fresh  Waters. 
A.    Superficial  Waters,  or  Rivers. 

The  mechanical  effects  of  fresh  waters  are  - 

1.  Erosion. 

2.  Transportation  of  earth,  gravel,  stones,  etc. 

3.  Distribution  of  the  transported  material,  and  formation 
of  fragmental  deposits. 

I .  Erosion. 

The  waters  of  rivers  descend  in  the  form  of  rain  and  snow 
from  the  clouds,  and  are  derived  by  evaporation  both  from 
the  surface  of  the  land,  with  its'  lakes,  rivers,  and  foliage,  and 
from  the  ocean,  but  mostly  from  the  latter.  The  waters  rise 
into  the  upper  regions  of  the  atmosphere,  and,  becoming  con- 


276  DYNAMICAL   GEOLOGY. 

densed  into  drops  or  snow-flakes,  fall  over  the  hills  and  plains. 
They  gather  first  into  rills ;  these,  as  they  descend,  unite  into 
rivulets ;  these,  again,  if  the  region  is  elevated  or  mountain- 
ous, into  torrents ;  torrents,  flowing  down  the  different  moun- 
tain valleys,  combine  with  other  torrents  to  form  rivers ;  and 
rivers  from  one  mountain-chain  sometimes  join  the  rivers 
from  another  and  make  a  common  stream  of  great  magnitude, 
like  the  Mississippi  or  the  Amazon. 

The  Mississippi  has  its  tributaries  among  all  the  eastern 
heights  of  the  great  Rocky  Mountain  chain,  throughout  a 
distance  of  1,000  miles,  or  between  the  parallels  of  35°  N. 
and  50°  N. ;  and  still  another  set  of  tributaries  gather  waters 
from  the  Appalachian  chain,  between  Western  New  York  and 
Alabama,  Rills,  rivulets,  torrents,  and  rivers  combine  over 
an  area  of  millions  of  square  miles  to  make  the  great  central 
trunk  of  the  North  American  continent. 

The  amount  of  water  poured  each  year  into  the  ocean  by 
the  Mississippi  averages  19J  trillions  (19,500,000,000,000) 
cubic  feet,  varying  from  11  trillions  in  dry  years  to  27  tril- 
lions in  wet  years.  This  amount  is  about  one  quarter  of  that 
furnished  by  the  rains,  the  rest  being  lost  mostly  by  direct 
evaporation,  but  also  in  part  by  absorption  into  the  soil  and 
by  contributing  to  the  growth  of  vegetation. 

Erosion  or  wear,  termed  also  denudation,  goes  on  wherever 
the  waters  have  motion.  The  rain-drop  makes  an  impression 
where  it  falls  (Fig.  21,  page  34) ;  the  rill  and  rivulet  carry 
off  light  sand  and  deepen  their  beds,  as  may  be  seen  on  any 
sand-bank  or  by  many  a  roadside;  torrents  work  with  far 
greater  power,  tearing  up  rocks  and  trees  as  they  plunge 
along,  and,  in  the  course  of  time,  making  deep  gorges  or  val- 
leys in  the  mountain-slopes ;  and  rivers,  especially  in  periods 
of  flood,  hurry  on  with  vast  power,  making  wider  valleys  over 
the  breadth  of  a  continent. 

The  slopes  of  a  lofty  mountain,  exposed  through  ages  to 
the  action  described,  finally  become  reduced  to  a  series  of 
valleys  and  ridges,  and  the  summit  often  to  towering  peaks 


WATER.  277 

and  crested  heights,  —  all  these  effects  originating  in  the  fall 
of  rain-drops  or  snow-flakes. 

Nearly  all  the  deep  valleys  of  the  world  owe  their  excava- 
tion to  running  water.  Their  positions  have  sometimes  been 
determined  by  the  courses  of  fissures  in  the  earth's  strata  or 
of  downward  bendings  in  the  earth's  crust  (geosynclinals) ; 
but,  generally,  rivers  have  worked  out  their  own  channels  from 
their  beginnings  onward  to  their  present  depth  and  extent. 

The  tendency  of  many  rocks  to  decompose,  or  fall  to  pieces 
from  weathering,  aids  the  waters  in  producing  their  mechanical 
effects.  They  have  been  at  times  further  aided  by  glaciers, 
as  explained  beyond. 

Where  the  stream  has  a  rapid  descent,  and  is  therefore  a 
torrent,  it  plunges  on  with  great  violence  and  erodes  mainly 
along  its  bottom.  Lower  down  the  mountain,  where  the  slope 
of  its  bed  is  gentle,  it  becomes  more  quiet,  and  excavates  but 
slightly,  if  at  all,  at  bottom.  In  its  floods,  however,  it  spreads 
beyond  its  banks,  and  tears  away  the  earth  or  rocks  either 
side,  encroaching  on  the  hills  and  making  for  itself  a  broad 
flat,  or  flood-plain.  As  the  floods  cease,  the  stream  becomes 
again  confined  to  its  channel.  Every  river  has  thus  its  channel 
for  the  dry  season,  and  its  flood-plain  which  it  covers  in  times 
of  overflowing. 

The  great  rivers  of  the  continents,  as  well  as  the  streamlets 
along  roadsides,  illustrate  this  subject.  Wherever,  in  countries 
that  have  rain,  there  is  a  ridge,  be  it  small  or  large,  there  are 
gullies,  or  gorges,  or  valleys ;  and  if  any  of  its  streams  are 
followed  up  to  their  head,  there  will  be  found,  first,  the  chan- 
nel and  its  bordering  flood-plain ;  then  the  narrower  valley 
with  the  hurrying  torrent,  sometimes  plunging  in  cataracts, 
and  receiving  smaller  torrents  along  its  course  ;  then,  toward 
the  top,  the  torrent  dwindling  to  a  rivulet,  or,  if  the  summit 
is  nearly  flat  and  wooded,  there  may  be  at  top  wet  swampy 
land  or  lakes. 

A  cascade  usually  occurs  on  a  rapid  stream,  where  in  the 
course  of  it  there  is  a  hard  bed  of  rock  overlying  a  soft  one. 


278 


DYNAMICAL   GEOLOGY. 


The  hard  bed  resists  wear,  while  the  soft  one  below  yields 
easily :  thus  a  plunge  begins,  which  increases  in  force  as  it 
increases  in  extent.  The  rills  and  rivulets  made  by  a  shower 
of  rain  along  roadsides  or  sand-banks  often  illustrate  also  this 
feature  of  the  great  mountain  streams. 

When  the  rocks  underlying  a  region  are  nearly  horizontal, 
the  valleys  cut  by  the  rivers  have  usually  bold  rocky  sides. 
In  many  parts  of  the  Eocky  Mountains  the  streams  have 
worked  their  way  down  through  the  rocks  for  hundreds,  and 

Fig.  385. 


Canon  of  the  Colorado. 

at  times  even  thousands,  of  feet.     Such  a  place  is  often  called 
a  canon  (pronounced  as  if  spelled  canyon). 

These  canons  are  of  wonderful  depth  and  magnitude  on  the 
Colorado  Eiver,  over  the  west  slope  of  the  Eocky  Mountains, 
between  longitude  111°  W.  and  115°  W.  For  300  miles  there 


WATER.  279 

is,  as  stated  by  Dr.  Newberry,  a  nearly  continuous  canon, 
3,000  to  6,000  feet  deep.  The  annexed  sketch,  from  one  of 
the  excellent  photographs  of  the  region  by  the  artist  of  Pow- 
ell's Expedition,  represents  a  portion  of  it,  called  the  Marble 
Canon.  The  rocks  stand  in  nearly  vertical  precipices  either 
side  of  the  stream,  and  the  height  above  the  water  to  the  top 
of  the  bluff  seen  in  the  distance  is  3,500  feet.  The  deep 
gorge  is  the  result,  as  stated  by  Dr.  Newberry,  of  erosion  by 
the  stream,  which  is  still  continuing  its  wearing  action. 
Over  the  upper  country,  not  far  from  the  canon,  there  are 
many  flat-topped  hills,  or,  rather,  mountains,  in  which  the 
strata  are  piled  up  another  3,500  feet,  and  in  some  places 
5,000 ;  which  are  portions  the  eroding  waters  have  left  of 
great  formations  that  once  spread  over  the  whole  region. 

The  rocky  gorge,  seven  miles  long  and  200  to  250  feet  deep, 
in  which  the  Niagara  River  flows  in  violent  rapids  after  its 
plunge  at  the  great  fall,  is  believed  with  reason  to  have  been 
made  by  the  waters,  and  mainly  through  the  action  of  the 
plunging  stream  at  the  fall.  Every  year  rocks  are  under- 
mined and  tumbled  down  into  the  depths  below,  and  thus 
the  position  of  the  fall  is  slowly  changing,  moving  higher  and 
higher  up  stream  with  the  successive  years.  The  rock,  for 
half  the  height  of  the  fall,  or  80  feet,  is  of  hard  limestone ; 
but  the  lower  half  is  of  soft  shale,  and,  being  easily  worn 
away  by  the  waters,  it  undermines  the  limestone  and  thus 
hastens  the  movement. 

The  deep  channellings  or  sculpturing  such  strata  have 
undergone  has  often  reduced  an  elevated  region,  which  was 
level  when  lifted  from  the  ocean,  to  a  collection  of  lofty 
mountain-peaks  and  ridges,  each  carved  out  by  the  water,  — 
or  a  result  of  circumdenudation, 

The  following  figures,  by  Lesley,  illustrate  some  of  the 
results  of  the  sculpturing  by  water  of  strata,  —  both  hori- 
zontal strata,  and  upturned  or  flexed.  In  the  production 
of  such  elevations,  the  ocean  has  sometimes  taken  part  dur- 
ing the  submergence  of  a  continent ;  but  the  final  results  are, 


280 


DYNAMICAL   GEOLOGY. 


in  almost  all  cases,  due  to  the  chisellings  of  fresh  waters. 
The  figures  here  given  are  small,  but  the  elevations  they 
represent,  as  illustrated  in  the  Appalachians,  Juras,  and  many 
other  mountain  regions,  are  often  some  thousands  of  feet  in 
height. 

When  the  beds  are  horizontal,  or  nearly  so,  but  of  unequal 
hardness,  the  softer  strata  are  easily  worn  away,  and  by  this 
means  the  harder  strata  become  undermined.  Table-lands 
are  often  thus  formed  having  a  top  of  the  harder  rock,  and 
the  declivities  usually  banded  with  projecting  shelves  and  in- 
tervening slopes.  Figs.  386,  387  represent  the  common  char- 


Fig.  386. 


Fig.  387. 


acter  of  such  hills.  Such  flat-topped  elevations  in  the  Col- 
orado region  have  been  called  Mesas,  from  the  Spanish  for 
table. 

When  the  beds  are  inclined  between  5°  and  30°,  and  are 
alike  in  hardness,  there  is  a  tendency  to  make  hills  with  a 
long  back  slope  and  bold  front ;  but  with  a  much  larger  dip, 
the  rocks,  if  hard,  often  outcrop  in  naked  ledges. 

When  the  dipping  strata  are  of  unequal  hardness,  and  lie 
in  folds,  there  is  a  wide  diversity  in  the  results  on  the  fea- 
tures of  the  landscape. 

Figs.  388,  389  represent  the  effects  from  the  erosion  of  a 
synclinal  region  consisting  of  alternations  of  hard  and  soft 
strata.  The  protection  of  the  softer  beds  by  the  harder  is 

Figs.  388-393. 


well  shown.     This  is  still  further  exhibited  in  Figs.  390  - 
393. 


WATER. 


281 


Anticlinal  strata  give  rise  to  another  series  of  forms,  in 
part  the  reverse  of  the  preceding,  and  equally  varied.  Figs. 
394-397  represent  some  of  the  simpler  cases.  When  the 
back  of  an  anticlinal  mountain  is  divided  (as  in  Figs.  394, 
395,  396),  the  mountain  loses  the  anticlinal  feature,  and  the 


Figs.  394-397. 


parts  are  simply  monoclinal  ridges.  In  Fig.  397  the  anticlinal 
character  is  distinct  in  the  central  portion,  while  lost  in  the 
parts  either  side.  In  Fig.  397,  to  the  right,  a  common  effect 
is  shown  of  the  protection  afforded  to  softer  layers  by  even  a 
vertical  layer  of  hard  rock :  the  vertical  layer  forms  the  axis 
of  a  low  ridge. 

2.  Transportation  by  Rivers,  and  distribution  of  trans- 
ported Material. 

1.  Fact  of  transportation.  —  It  has   been   stated   that   the 
massive  mountains  have  been  eroded  into  valleys  and  ridges 
by  running  water.     The  material  worn  out  has  been  trans- 
ported somewhere  by  the  same  waters. 

Part  of  the  transported  material  in  all  such  operations 
goes  to  form  the  great  alluvial  plains  that  occupy  the  river- 
valleys  throughout  their  course.  Part  is  carried  on  to  the  sea 
into  which  the  river  empties,  where  it  meets  the  counteracting 
waves  and  currents  and  is  distributed  for  the  most  part  along 
the  shores,  filling  estuaries  or  bays,  or  making  deltas,  and  ex- 
tending the  bounds  of  the  land. 

Thus  the  mountains  of  a  continent  are  ever  on  the  move 
seaward,  and  contribute  to  the  enlargement  of  the  sea-shore 
plains.  The  continent  is  losing  annually  in  mean  height,  but 
gaining  in  width  or  extent  of  dry  land. 

2.  The  transporting  power   of   water.  —  The   transporting 
power  of  running  water  is  very  great  when  the  flow  is  rapid. 


282  DYNAMICAL  GEOLOGY. 

Large  stones  and  masses  of  rocks  are  torn  up  and  moved  on- 
ward by  the  mountain-torrent;  pebbles,  when  the  current 
runs  but  a  few  miles  per  hour;,  and,  at  slower  rates,  gravel, 
sand,  or,  when  very  slow,  only  fine  clay.  Hence,  as  a  stream 
loses  in  rapidity  of  movement,  it  leaves  behind  the  coarser 
material,  and  carries  only  the  finer ;  if  the  rate  becomes  very 
slow,  it  drops  the  gravel  or  the  sand,  and  bears  on  only  the 
finest  earth  or  clay. 

Consequently,  where  the  current  is  swift,  the  bottom  (and 
the  shores  also  whenever  the  current  strikes  them)  is  stony  or 
pebbly ;  and  where  the  water  is  still,  or  nearly  so,  the  bottom 
and  shores  are  muddy. 

The  larger  part  of  the  transportation  by  rivers  is  done  in 
their  seasons  of  flood.  Then  it  is  that  streams  are  muddy 
with  the  earth  they  are  bearing  along. 

3.  Wearing  action  of  the  transported  material  —  The  stones 
are  not  only  transported  by  the  waters,  but  by  the  mutual 
friction  thus  produced  they  are  made  into  rounded  stones  and 
reduced  to  pebbles  and  earth.      The  rounded  stones,  gravel, 
and  earth  of  fields  and  gardens  over  the  globe,  and  also  the 
material  of  all  geological  formations,  has  been  made  out  of 
pre-existing   solid  rocks   to  a  large  degree   by  the  wearing 
action  of  waters,  —  either  those  of  streams  over  the  land,  or 
those  of  the  ocean.     But  this  action  is  greatly  aided  in  places 
by  the  partial  decomposition  or  disaggregation  due  to  the  ele- 
ments.    This  last-mentioned  cause  is  sufficient  alone  to  turn 
angular  blocks  of  most  rocks  into  rounded  masses. 

The  finer  transported  material  is  called  detritus  (from  the 
Latin  for  worn  out),  and  also  silt.  The  rounded  stones  are 
termed  bowlders. 

4.  Amount  of  material  transported.  —  The  amount  of  trans- 
ported material  varies  with  the  size  and  current  of  the  rivers 
and  the  kind  of  country  they  flow  through.     The  Mississippi 
carries  annually  to  the  Gulf  of  Mexico,  according  to  Hum- 
phreys and  Abbot,  on  an  average,  812,500,000,000  pounds  of 
silt,  —  equal  to  a  mass  one  square  mile  in  area  and  241  feet 


WATER. 


283 


deep,  —  and  its  bottom-waters  push  on  enough  more  to  make 
the  241  feet  268  feet.  The  total  annual  discharge  of  silt  by 
the  Ganges  has  been  estimated  at  6,368,000,000  cubic  feet. 

5.  Alluvial  formations.  —  The  deposits  made  by  the  trans- 
ported material  which  now  constitute  the  alluvial  plains  of 


the  river- valleys  cover  a  large  part  of  a  continent,  since  rivers 
or  smaller  streams  are  almost  everywhere  at  work.  They  are 
made  up  of  layers  of  pebbles  or  gravel,  and  of  earth,  silt,  or 


284  DYNAMICAL   GEOLOGY. 

clay,  especially  of  these  finer  materials.  Logs,  leaves,  shells, 
and  bones  occur  in  them ;  but  these  are  rare ;  for  whatever 
floats  down  stream  is  widely  scattered  by  the  waters,  and  to 
a  great  extent  destroyed  by  wear  and  decay. 

6.  Estuary  and  Delta  formations.  —  The  detritus-material 
discharged  by  the  river  at  its  mouth  tends  to  fill  up  the 
bay  into  which  it  empties,  and  make  wide  flats  on  its 
borders,  and  thus  contract  it  to  the  breadth  merely  of  the 
river-current. 

Where  the  tides  are  feeble  and  the  river  large,  the  depos- 
its about  the  mouth  of  the  stream  gradually  encroach  on  the 
ocean,  and  make  great  plains  and  marshy  flats,  which  are 
intersected  by  the  many  mouths  of  the  river  and  a  network 
of  cross-channels.  Such  a  formation  is  called  a  delta.  Fig. 
398  represents  the  delta  of  the  Mississippi,  the  white  lines 
being  the  water-channels  and  the  black  the  great  alluvial 
plains.  The  delta  properly  commences  below  the  mouth  of 
Red  River,  where  the  Atchafalaya  bayou,  or  side-channel  of 
the  river,  begins.  The  whole  area  is  about  12,300  square 
miles ;  about  one  third  is  a  sea  marsh,  only  two  thirds  lying 
above  the  level  of  the  Gulf. 

The  deltas  of  the  Nile,  Ganges,  and  Amazon  are  similar  in 
general  features  to  that  of  the  Mississippi. 

The  detritus  poured  into  the  ocean  where  the  tides  or  cur- 
rents are  strong,  and  a  considerable  part  of  that  where  the 
tides  are  feeble,  goes  to  form  sea-shore  flats  and  sand-banks 
and  off-shore  deposits.  In  their  formation  the  ocean  takes 
part  through  its  waves  and  currents;  and  hence  they  are 
more  conveniently  described  in  connection  with  the  remarks 
on  oceanic  action. 

B.    Subterranean  "Waters. 

1.  Origin  and  course  of  subterranean  waters,  — A  part  of  the 
waters  that  fall  on  the  earth's  surface  —  on  its  mountains  as 
well  as  its  plains  —  sinks  through  the  ground  and  often  pene- 
trates to  unknown  depths  between  the  strata  or  their  layers. 


WATER. 


285 


Fig.  399. 


Section  illustrating  the  origin  of  Artesian  wells. 


Such  underground  waters  become  underground  streams ;  and, 
as  their  channels  are  surrounded  by  rocks,  the  water  flows 
actually  in  a  tube.  When,  therefore,  they  have  their  source 
in  elevated  regions,  the  pressure  increases  with  the  descent, 
and  wherever  an  opening  in  the  country  below  gives  them  a 
chance  of  escape  they  often 
come  out  with  great  force. 
By  boring  down  through 
the  rocks,  such  an  under- 
ground stream  may  be 
struck  in  almost  any  region, 
and  frequently  the  water 
will  rise  and  rush  out  of  the 
opening  in  a  jet  of  great 
height.  In  Fig.  399  the 
underground  waters  are  supposed  to  enter  at  a,  along  a  clayey 
layer  (for  clayey  layers  hold  the  water,  while  it  will  soak 
through  a  sandy  one)  and  under  another  layer  that  is  not 
very  porous ;  it  escapes  by  the  boring  I  c,  and  is  thrown  up 
in  a  jet  to  d.  There  is  so  much  friction  along  the  bed  of 
the  stream  in  the  course  of  its  descent,  that  the  height  of  the 
jet  is  always  much  less  than  the  whole  descent,  or  b  e. 

Such  wells  are  usually  called  Artesian  wells  or  borings,  from 
the  district  of  Artois  in  France,  where  they  were  early  made. 
The  Artesian  well  of  Grenelle  in  Paris  is  1,798  feet  deep,  and 
when  first  made  the  water  darted  out  to  a  height  of  112  feet. 
One  at  St.  Louis  has  a  depth  of  3,843J  feet,  but  without  get- 
ting water,  because  the  region  for  many  miles  around  is  one 
of  horizontal  rocks.  The  horizontal  beds  continued  to  the 
bottom  of  the  boring,  where  the  Lower  Silurian  strata  are 
in  contact  with  the  Archaean.  Such  wells  are  used  for  agri- 
cultural and  manufacturing  purposes. 

The  underground  waters  often  gush  out  along  a  sea-shore, 
or  from  beneath  the  sea ;  and  sometimes  in  so  great  volume 
that  vessels,  at  certain  seasons,  are  enabled  to  take  in  fresh 
water  from  alongside  while  lying  off  in  a  harbor. 


286  DYNAMICAL  GEOLOGY. 

They  flow  and  have  cascades  in  many  caverns,  as  in  the 
Mammoth  Cave,  Kentucky,  the  Adelberg  Cave  near  Trieste 
in  Austria,  and  many  others.  In  some  cases  they  come  out 
to  the  surface  in  sufficient  volume  to  turn  a  mill,  and  are  set 
to  work  immediately  on  their  showing  themselves. 

2.  Erosion.  —  Subterranean  waters  have  eroding  and  trans- 
porting power,  as  well  as  those  of  the  land,  and  may  excavate 
large  channels.     They  may,  by  undermining,  lead  to  the  fall- 
ing of  extensive  areas  of  rock  or  to  long  fractures,  either 
superficial  or  subterranean ;  and  in  the  case  of  the  latter,  the 
catastrophe  may  be  announced  at  the  surface  only  by  vibra- 
tions, that  is,  feeble  earthquakes. 

3.  Land-Slides.  —  Land-Slides  are  of  different  kinds  :  — 

1.  The  sliding  of  the  surface  earth,  or  gravel,  of  a  hill  down 
to  the  plain  below.     This  effect  may  be  caused  by  the  waters 
of  a  severe  storm  wetting  the  material  deeply  and  giving  it 
greatly  increased  weight,  besides  loosening  its  attachment  to 
the  more  solid  mass  below. 

2.  The  sliding  down  a  declivity  to  the  plain  below  of  the 
upper  layer  of  a  rock-formation.     This  may  happen  when  this 
upper  layer  rests  on  a  clayey  or  sandy  layer  and  the  latter 
becomes  very  wet  and  greatly  softened  by  the  waters ;  the 
upper  layer  slides  down  on  the  softened  bed. 

3.  The  settling  of  the  ground  over  a  large  area.     This  may 
take  place  when  a  layer  of  clay  or  loose  sand  becomes  wet 
and  softened  by  percolating  waters,  and  then  is  pressed  out 
laterally  by  the  weight  of  the  superincumbent  layers.     But 
such  a  result  is  not  possible  unless  there  is  a  chance  for  the 
wet  layer  to  move  or  escape  laterally.     Sometimes  part  of  a 
wet  clayey  layer,  pressed  to  one  side  in  this  way,  is  left  very 
much  folded,  while  the  associated  sandy  layers  have  their  usual 
regular  bedding. 

2.    The  Ocean. 

The  ocean  is  vast  in  extent  and  vast  in  the  power  which 
it  may  exert.     But  its  mechanical  work  in  Geology  is  mostly 


WATER.  287 

confined  to  its  coasts  and  to  soundings,  where  alone  material 
exists  in  quantity  within  reach  of  the  waves  or  currents.  In 
ancient  time,  when  the  continents  had  not  their  present 
mountains,  and  were  to  a  great  extent  submerged  at  shallow 
depths,  this  work  was  performed  simultaneously  over  a  large 
part  of  their  surface,  and  strata  nearly  of  continental  area 
were  sometimes  formed.  In  the  present  age,  oceanic  action 
is  confined  to  the  borders  of  the  continents. 

The  mechanical  effects  of  the  ocean  are  produced  by  its 
waves  and  currents. 

I.  Erosion  and  Transportation. 

1.  Waves.  —  7.  General  action.  —  The   oceanic  waves  are  a 
constant  force.     Night  and  day,  year  in  and  year  out,  with 
hardly  an  intermission,  they  break  against  the  beaches  and 
rocks  of  the  coast;  sometimes  gently,  sometimes  in  heavy 
plunges  that  have  the  force  of  a  Niagara  of  almost  unlimited 
breadth.     The  gentlest  movements  have  some  grinding  action 
among  the  sands,  while  the  heaviest  may  dislodge  and  move 
along,  up  the  shores,  rocks  many  tons  in  weight.     Niagara 
wastes  its  power  by  falling  into  an  abyss  of  waters :  while 
in  the  case  of  the  waves  the  rocks  are  bared  anew  for  each 
successive  plunge.     Cliffs  are  undermined,  rocks  are  worn  to 
pebbles  and  sand,  and   sand   ground   to   the   finest  powder. 
Rocky  headlands  on  windward .  coasts  are  especially  exposed 
to  wear,  since  they  are  open  to  the  battering  force  from  dif- 
ferent directions. 

2.  Level  of  greatest  eroding  Fig*  40°* 
action.  —  The  eroding  action  is 

greatest  for  a  short  distance 
above  the  height  of  half-tide, 
and,  except  in  violent  storms, 
it  is  almost  null  below  low- 

Cliff,  New  South  Wales. 

tide  level.     Fig.  400  represents 

in  profile  a  cliff,  having  its  lower  layers,  near  the  level  of 

low  tide,  extending  out  as  a  platform  a  hundred  yards  wide. 


288  DYNAMICAL  GEOLOGY. 

As  the  tide  commences  to  move  in,  the  waters,  while  still 
quiet,  swell  over  and  cover  this  platform,  and  so  give  it  their 
protection ;  and  the  force  of  wave-action,  which  is  greatest 
above  half-tide,  is  mainly  expended  near  the  base  of  the  cliff, 
just  above  the  level  of  the  platform. 

3.  Action  landward. — Waves   on   shallow   soundings   have 
some  transporting  power ;  and,  as  they  always  move  toward 
the  land,  their  action  is  landward.     They  thus  beat  back,  little 
by  little,  any  detritus  in  the  waters,  preventing  that  loss  to 
continents  or  islands  which  would  take  place  if  it  were  car- 
ried out  to  sea. 

4.  Effect  on  the  outline  of  coasts.  —  No  excavation  of  narrow 
valleys.  —  As  the  action  of  waves  on  a  coast  tends  to  wear 
away  headlands,  and  at  the  same  time  to  fill  up  bays  with 
detritus,  it  usually  results  in  making  the  outline  more  regular 
or  even.     There  is  nowhere  a  tendency  to  excavate  narrow 
valleys  into  a  coast,  like  those  occupied  by  rivers.     Such  val- 
leys are  made  by  the  waters  of  the  land ;  for  the  ocean  can 
work  at  valley-making  only  when  it  has  already  an  open 
channel  for  the  waters  to  pass  through,  and  then  the  valleys 
are  of  very  great  width.     If  a  continent  were  sinking  slowly  in 
the  ocean,  or  rising  slowly  from  it,  wave-action  would  still  be 
attended  by  the  same  results ;  for  each  part  of  the  surface 
would  be  successively  a  coast-line,  and  over  each  there  would 
be  the  same  wearing  away  of  headlands  and  filling  of  bays, 
instead  of  the  excavation  of  valleys.     See  further,  on  this 
subject,  page  280. 

2.  Tidal  currents,  —  Tidal  currents  often  have  great  strength 
when  the  tide  moves  through  channels  or  among  islands,  and 
then  they  are  a  means  of  erosion  and  transportation  daily  in 
action,  wherever  there  is  rock,  mud,  or  sand  within  their  reach, 
as  is  usually  the  case  in  the  vicinity  of  the  land. 

The  out-flowing  current,  or  that  connected  with  the  ebbing 
tide,  is  deeper  in  its  action,  and  has,  therefore,  more  excavating 
and  more  transporting  power,  than  the  in-flowing,  or  that  of 
the  incoming  tide.  The  latter  moves  on  as  a  great  swelling 


WATER.  289 

wave,  and  fills  the  bays  much  above  their  natural  level ;  but 
the  out-flowing  current  begins  along  the  bottom  in  bays  before 
the  tide  is  wholly  in,  owing  to  the  accumulation  of  waters, 
and  when  the  tide  changes  it  adds  to  the  strong  current-move- 
ment already  in  progress. 

The  piling  up  of  the  waters  in  a  bay  by  the  tides,  or  by 
storms,  produces,  especially  if  the  entrance  is  not  very  broad, 
a  strong  out-flowing  current  at  bottom,  which  tends  to  keep 
the  channel  deep  and  clear  of  obstructions. 

The  bore  or  eagre  of  some  great  rivers  is  a  kind  of  tidal 
flow  up  a  stream.  It  is  produced  when  the  regular  rise  of 
the  tide  in  the  bay  at  the  mouth  of  the  river  is  obstructed 
by  the  form  of  the  entrance  and  its  sand-banks,  together  with 
the  outflow  of  the  river,  so  that  the  waters  are  for  a  while 
prevented  from  entering,  until,  finally,  all  those  of  one  tide 
rush  in  at  once,  or  in  a  few  great  waves.  The  eagres  of  the 
Amazon,  the  Hoogly  in  India  (one  of  the  mouths  of  the 
Ganges),  and  the  Tsien-tang  in  China,  are  among  the  most 
remarkable.  In  the  case  of  the  Tsien-tang,  the  water  moves 
up  stream  in  one  great  wave,  plunging  like  an  advancing 
cataract,  four  or  five  miles  broad  and  30  feet  high,  at  a  rate 
of  25  miles  an  hour.  The  boats  in  the  middle  of  the  stream 
simply  rise  and  fall  with  the  passage  of  the  wave,  being 
pushed  forward  only  a  short  distance ;  but  along  the  shores 
there  is  often  great  devastation,  the  banks  being  worn  away 
and  animals  sometimes  surprised  and  destroyed. 

3.  Currents  made  by  winds.  —  There  are  also  currents  pro- 
duced  ly  winds,  especially  when  there  are  long  storms,  or 
when  the  winds  blow  for  months  in  one  direction.  The  great 
currents  of  the  oceans,  such  as  the  Gulf  Stream,  are  attributed 
by  some  physicists  to  this  source.  Such  currents,  sweeping 
by  an  island,  transport  from  one  place  to  another  in  their 
course  more  or  less  of  the  sand  of  the  shores,  and  the  same 
sand  may  be  in  part  carried  back  again  when  the  season 
changes  to  that  in  which  the  wind  blows  from  the  opposite 
direction.  Other  portions  of  detritus  may  be  carried  by 

13 


290  DYNAMICAL   GEOLOGY. 

them  away  from  the  island  and  distributed  in  the  deeper 
waters. 

The  great  currents  of  the  ocean  are  for  the  most  part  so 
distant  from  the  borders  of  the  continents  that  little  detri- 
tus conies  within  their  reach.  As  these  currents  have  great 
depth,  —  often  a  thousand  feet  or  more,  —  their  course  is  de- 
termined by  the  deep-water  slopes  of  the  submerged  border 
of  a  continent,  so  that  when  the  submerged  border  is  shallow 
for  a  long  distance  out  (as  off  New  Jersey  and  Virginia,  where 
this  long  distance  is  even  50  to  80  miles),  the  current  is 
equally  remote,  and  exerts  very  feeble  if  any  action  near  the 
shores.  Wherever  it  actually  sweeps  close  along  a  coast,  it 
may  bear  away  some  detritus  to  drop  it  over  the  bottom  in 
the  neighboring  waters. 

The  oceanic  currents  flowing  from  polar  seas  produce  im- 
portant effects  by  means  of  the  icebergs  which  they  bear  into 
warmer  latitudes.  These  icebergs  are  freighted  with  thousands 
of  tons  of  earth  and  rocks  ;  and  wherever  they  melt,  they 
drop  all  to  the  ocean's  bottom.  The  sea  about  the  Newfound- 
land banks  is  one  of  the  regions  of  the  melting  icebergs ;  and 
there  is  no  doubt  that  vast  submarine  accumulations  of  such 
material  have  been  there  made  by  this  means.  It  has  been 
suggested  that  the  banks  may  have  been  thus  formed. 

2.  Distribution  of  material,  and  the  formation  of  marine 
and  fluvio-marine  deposits. 

1.  Origin  of  material  —  The  material  used  by  the  waves 
and  currents  is  either  —  (1)  the  stones,  gravel,  sand,  clay,  or 
earth  produced  by  the  wear  of  coasts;  or  (2)  the  detritus 
brought  down  by  rivers  and  poured  into  the  ocean,  as  ex- 
plained on  page  281. 

The  latter,  in  the  present  age,  is  vastly  the  most  important. 
But  in  the  earlier  geological  ages,  when  the  dry  land  was  of 
small  extent,  rivers  were  small  and  were  but  a  feeble  agency. 
The  ocean  had  then  vastly  greater  advantages  than  now,  be- 
cause, as  stated  on  page  83,  the  continents  were  mostly  sub- 


WATER.  291 

merged  at  shallow  depths,  or  lay  near  tide-level  within  reach 
of  the  waves  and  currents. 

The  decomposition  or  disintegration  of  exposed  rocks 
through  the  agency  of  air  and  moisture  must  have  aided  in 
degradation  formerly  more  than  now,  since  in  Paleozoic  time, 
and  earlier,  carbonic  acid  gas,  the  chief  agent  of  destruction, 
was  much  more  abundant  in  the  atmosphere  than  it  is  now. 
This  agent  is  carried  to  the  earth's  surface  by  the  rains,  and  it 
is  still  effective  in  the  decomposition  of  granite,  gneiss,  and 
many  other  rocks. 

2.  Forces  in  action.  —  In  the  distribution  of  the  material, 
the  waves  and  marine  currents  have  either  worked  alone,  in 
the  manner  explained  on  the  preceding  pages,  or  in  conjunc- 
tion with  river-currents  wherever  these  existed. 

3.  Marine  formations.  —  The  marine  formations  are  of  the 
following  kinds  :  — 

7.  Beach-accumulations.  —  Beaches  are  made  of  the  material 
borne  up  the  shores  by  the  waves  and  tides  and  left  above 
tide-level.  This  material  consists  of  stones  or  pebbles,  sand, 
mud,  earth,  or  clay.  It  is  coarse  where  the  waves  break 
heavily,  because,  although  trituration  to  powder  is  going  on 
at  all  times,  the  powerful  wave-action  and  the  undercurrent 
carry  off  the  finer  material  into  the  off-shore  shallow  waters, 
where  it  settles  over  the  bottom  or  is  distributed  by  currents. 
It  is  fine  where  the  waves  are  gentle  in  movement,  as  in  shel- 
tered bays,  or  estuaries,  the  triturated  material  remaining  in 
such  places  near  where  it  is  made,  and  often  being  the  finest 
of  mud. 

2.  Sand-banks,  or  reefs. — Shallow-water  accumulations.  —  Shal- 
low-water accumulations  may  be  produced  in  bays,  estuaries, 
or  the  inner  channels  of  a  coast,  and  over  the  bottom  outside. 
They  consist  usually  of  coarse  or  fine  sand  and  earthy  de- 
tritus, but  may  include  pebbles  or  stones  when  the  currents 
are  strong.  The  material  constituting  them  is  derived  from 
the  land  through  the  wearing  and  transporting  action  of  the 
waves  and  currents.  The  accumulations  mav  increase  under 


292  DYNAMICAL  GEOLOGY. 

wave-action  in  shallow  water,  until  they  approach  or  rise 
above  low-tide  level,  and  then  they  form  sand-banks.  Such 
sand-banks  keep  their  place  in  the  face  of  the  waves,  for  the 
same  reason  as  the  platform  of  rock  mentioned  on  page  287 
and  illustrated  in  Fig.  400. 

3.  Fluvio- marine  formations.  — Most  of  the  accumulations  in 
progress  on  existing  shores,  whether  sand-banks,  or  estuary, 
or  off-shore  deposits,  especially  about  well- watered  continents, 
contain  more  or  less  of  river-detritus,  and  are  modified  in 
their  forms  by  the  action  of  river-currents.  Along  the  whole 
eastern  coast  of  the  United  States  south  of  New  England, 
and  on  all  the  borders  of  the  Gulf  of  Mexico,  the  formations 
in  progress  are  mainly  fluvio-marine,  —  that  is,  the  combined 
result  of  rivers  and  the  ocean.  The  coast-region  on  the  con- 
tinent is  now  slowly  widening  through  this  means,  and  has 
been  widening  for  an  indefinite  period.  This  coast-region  is 
low,  flat,  often  marshy,  full  of  channels  or  sounds ;  and  facing 
the  ocean  there  is  a  barrier-reef,  made  of  sand. 

The  rivers  pour  out  their  detritus  especially  during  their 
floods,  and  the  ocean's  waves  and  currents  meet  it  as  the  tide 
sets  in  with  a  counter-action,  or  one  from  the  seaward ;  and 
between  the  two  the  waters  lose  in  rate  of  flow  and  drop  the 
detritus  over  the  bottom.  When  the  river  is  very  large  and 
the  tides  feeble,  the  banks  and  reefs  extend  far  out  to  sea. 
The  Mississippi  thus  stretches  its  many-branched  mouth 
(page  283)  fifty  miles  into  the  Gulf.  When  the  tide  is 
high,  sand-bars  are  formed;  and  the  higher  the  tides  the 
closer  are  the  sand-bars  to  the  coast.  When  the  stream  is 
small,  the  ocean  may  throw  a  sand-bank  quite  across  its 
mouth,  so  that  there  may  be  no  egress  to  the  river- waters  ex- 
cept by  percolation  through  the  sand,  or,  if  a  channel  is  left 
open,  it  may  be  only  a  shallow  one. 

3.   Structure  of  the  formations. 

Beach-formations  are  very  irregular  in  stratification  in  their 
upper  portions,  where  they  are  made  by  the  toss  of  the  waves 


WATER.  293 

and  the  drifting  by  winds  combined.  The  layers  —  as  shown 
in  Fig.  17  d,  page  32 —  have  but  little  lateral  extent,  and 
change  in  character  every  few  feet.  But  the  sloping  part  swept 
by  the  waves  below  high-tide  level  is  very  evenly  stratified 
parallel  to  the  surface ;  and  since  this  surface  pitches  at  an 
angle  usually  of  5°  to  8°,  the  beach-made  beds  have  the  same 
pitch  or  dip. 

The  sand-banks  and  reefs  made  in  shallow  waters  along 
a  coast  have  a  regular  and  more  horizontal  stratification,  and 
are  mostly  composed  of  sand  with  some  beds  of  pebbles.  They 
often  vary  much  every  mile  or  every  few  miles.  The  extent 
and  regularity  of  level  of  the  submerged  area  off  a  coast  will 
determine  in  a  great  degree  the  extent  to  which  the  uniform- 
ity of  stratification  may  extend ;  and  in  this  respect  the 
former  geological  ages,  as  observed  on  page  287  had  greatly 
the  advantage  of  the  present. 

Ripple-marks  (Fig.  18,  page  33)  are  made  by  the  wash  of  the 
waves  over  a  sand-flat  or  up  a  beach,  or  over  the  bottom 
within  soundings  where  the  depth  does  not  exceed  60  or 
80  fathoms.  Hill-marks  (Fig.  19)  are  produced  when  the 
return  waters  of  a  tide,  or  of  a  wave  that  has  broken  on  a 
beach,  flow  by  an  obstacle,  as  a  shell  or  pebble,  and  are  piled 
up  a  little  by  it  so  as  to  be  made  to  plunge  over  it  and  so 
erode  the  sands  for  a  short  distance  below  the  obstacle.  The 
oblique  lamination  in  a  layer,  or  ebb-and-flow  structure,  results 
from  the  rapid  inward  movement  of  the  tide,  or  the  flow  of 
any  current,  over  a  sandy  bottom :  it  makes  a  series  of  in- 
clined layers  by  the  piling  action;  when  the  movement 
ceases,  the  detritus  will  deposit  horizontally  for  a  while ;  and 
afterward  the  same  inward  movement  may  be  repeated,  pro- 
ducing anew  the  oblique  lamination.  When  there  are  plung- 
ing waves  accompanying  the  rapid  flow  of  a  current,  the 
obliquely  laminated  layer  is  broken  up  into  short  wave-like 
parts,  —  as  in  the  flow-and-plunge  structure  (page  32). 

The  imbedded  shells  and  other  animal  relics  in  a  beach  are 
worn  or  broken ;  those  in  the  bays  or  off-shore  shallow  waters 


294  DYNAMICAL   GEOLOGY. 

out  of  the  reach  of  the  waves  may  be  unbroken,  or  may  lie 
as  they  did  when  living ;  but  if  the  waters  are  not  so  deep 
but  that  the  shells  or  corals  are  exposed  to  wave-action,  they 
may  be  broken  or  worn  to  powder,  and  enter  in  this  state 
into  the  formation  in  progress.  (See  further,  page  271,  the 
remarks  on  the  formation  of  limestone  from  shells  or  corals.) 

Deposits  of  broken  shells  under  water  are  sometimes  made 
by  fishes  that  have  taken  the  animals  for  food.  Such  beds 
made  by  fishes  answer  to  the  shell-heaps  of  human  origin. 

In  the  sands  of  beaches  near  low-tide  level,  borings  of  Sea- 
worms,  or  of  some  Mollusks  or  Crustaceans,  may  exist. 

3.    Freezing  and  Frozen  Waters. 

A.    Freezing  Water. 

As  water  in  the  act  of  freezing  expands,  the  freezing  pro- 
cess, when  taking  place  in  the  seams  of  rock,  opens  the  seams 
and  tears  masses  asunder.  This  kind  of  action  is  especially 
destructive  in  the  case  of  rocks  that  are  much  fissured,  or  in: 
tersected  by  joints,  or  that  have  a  slaty  or  laminated  struc- 
ture. As  the  action  continues  through  successive  years  and 
centuries,  it  often  results  in  great  accumulations  of  broken 
stone.  The  slope,  or  talus,  of  fragments  at  the  foot  of  bluffs 
of  trap  or  basalt  is  often  half  as  high  as  the  bluff  itself.  In 
tropical  countries,  bluffs  have  no  such  masses  of  ruins  at  their 


Granular  rocks,  whether  crystalline  or  not,  when  they  read- 
ily absorb  water,  lose  their  surface-grains  by  the  same  freez- 
ing process.  Granite,  as  well  as  porous  sandstones,  may  thus 
be  imperceptibly  turning  to  dust,  earth,  or  gravel.  In  Alpine 
regions  this  action  may  be  incessant. 

B.    Frozen  Water. 

The  effects  of  ice  and  snow  are  conveniently  considered 
under  three  heads :  1.  The  ice  of  lakes  and  rivers ;  2. 
Glaciers;  3.  Icebergs. 


GLACIERS.  295 

I .  Ice  of  Lakes  and  Rivers. 

The  ice  of  lakes  and  rivers  often  forms  about  stones  along 
their  shores,  making  them  part  of  the  mass ;  and  other  stones 
sometimes  fall  on  the  surface  from  overhanging  bluffs.  In 
times  of  high  water,  or  floods,  the  ice,  rising  with  the  waters, 
may  carry  its  burden  high  up  the  shores,  or  over  the  flooded 
flats,  to  leave  them  there  as  it  melts ;  or,  if  within  reach  of 
the  current,  it  may  transport  the  stones  far  down  stream. 
This  is  a  common  method  of  transportation  by  ice.  Large 
accumulations  of  bowlders  are  sometimes  made,  by  this  means, 
on  the  shores  of  lakes,  far  above  the  ordinary  level  of  the 
waters. 

2.  Glaciers. 

1.  Glaciers  are  ice-streams,  or  rivers  in  which  the  moving 
material  is  frozen  instead  of  liquid  water. 

Like  large  rivers,  they  ordinarily  have  their  sources  in  high 
mountains,  and  descend  along  the  valleys ;  but  the  moun- 
tains are  such  as  take  snow  from  the  clouds  instead  of  rain, 
because  of  their  elevation ;  and  they  must  be  high  and  exten- 
sive enough  to  take  annually  a  large  supply  of  snow  from  the 
clouds^  so  that  the  snow  may  accumulate  to  a  great  depth. 

Like  large  rivers,  many  tributary  streams  coming  from  the 
different  valleys  unite  to  make  the  great  stream. 

As  with  rivers,  their  movement  is  owing  to  gravity,  or  to 
the  weight  of  the  material ;  but  the  average  rate  of  motion, 
instead  of  being  several  miles  an  hour,  is  generally  in  sum- 
mer but  10  to  18  inches  a  day,  or  a  mile  in  18  to  20  years. 
12  inches  a  year  corresponds  to  a  mile  in  14J  years.  The 
rate  is  half  less  in  winter  than  in  summer. 

As  with  rivers,  the  central  portions  move  most  rapidly,  the 
sides  and  bottom  being  retarded  by  friction. 

The  snow  of  the  mountain-tops,  called  the  n£v6,  which  is 
perhaps  hundreds  of  feet  deep,  becomes  compacted  and  con- 
verted into  ice  mainly  by  its  own  weight ;  and  thus  the  glacier 
begins.  Below  the  level  of  perpetual  frost  there  is  'occasional 


296  DYNAMICAL  GEOLOGY. 

melting  and  freezing,  and  by  these  means  the  change  to  ice 
is  made  more  complete.  As  the  glacier  starts  on  its  course, 
the  clouds  furnish  new  snows  to  keep  up  the  supply  and  help 
press  on  the  moving  mass. 

2.  Fractures  attending  the  movement  —  Crevasses,  —  Every 
valley  has  its  ridgy  sides,  its  sharp  turns,  its  abrupt  narrow- 
ings  and  widenings,  its  irregular  bottom ;   and  the  stiff  ice, 
compelled  to  accommodate  itself  to  these  irregularities,  has, 
consequently,  profound  crevasses  made  usually  along  its  bor- 
ders, besides  multitudes  of  cracks  that  are  not  visible  at  the 
surface;   also,   still  profounder   chasms  when  wrenched,   or 
stretched,  in  turning  some  point;  longer  crevasses,  crossing 
even  its  whole  breadth,  when  the  ice  plunges  down  a  steep 
place  in  an  ice-cascade,  or  when,  on  escaping  from  a  narrow 
gorge,  it  moves  off  freely  again  with  increase  of  slope.    Again, 
it  may  lose  all  its  crevasses,  from  their  closing  up,  when  the 
rate  of  motion  is  lessened  by  diminished  slope  or  otherwise. 

3.  Descent  below  the  snow-line.  —  The  height,  in  the  Alps, 
of  the  snow-line,  or  that  below  which  the  snow  annually  pre- 
cipitated melts  during  the  year,  is  8,000  feet  on  the  north  side 
of  the  Alps,  and  8,800  feet  on  the  south  side  ;  and  the  glacier 
descends  below  this  line  4,500  to  5,300  feet.     The  ice  resists 
the  melting  heat  of  summer  because  of  its  mass,  just  like  the 
ice  in  an  ice-house.     Though  starting  where  all  is  white  and 
barren,  it  passes  by  regions  of  Alpine  flowers,  and  often  con- 
tinues down  to  a  country  of  gardens  and  human  dwellings 
before  its  course  is  finally  cut  short  by  the  climate.     Thus, 
the  Bois  glacier,  an  upper  portion  of  which  is  called  the  Mer 
de  Glace,  rises  in  Mont  Blanc  and  other  neighboring  peaks, 
and  terminates,  like  two  other  glaciers,  in  the  vale  of  Cha- 
mouni.     In  a  similar  manner,  two  great  glaciers  descend  from 
the  Jungfrau  and  other  heights  of  the  Bernese  Alps  to  the 
plains  of  the  Grindelwald  Valley  just  south  of  Interlachen. 

Fig.  404  represents  one  of  the  ice-streams  of  the  Mount 
Rosa  region  in  the  Alps,  from  a  view  in  Professor  Agassiz's 
work  on  Glaciers.  It  shows  the  lofty  regions  of  perpetual 


GLACIERS. 


297 


snow  in  the  distance ;  the  bare  rocky  slopes  that  border  it, 
later  on  its  course ;  and  the  many  crevasses  that  intersect  the 
surface  of  the  ice-stream. 


Fig.  401. 


Glacier  of  Zermatt,  or  the  Gorner  Glacier. 

4.  Glacier  torrent,  —  The   melting   over  the   surface   of  a 
glacier  and  about  the  sides  of  its  crevasses  gives  origin  to  a 
stream  of  water  flowing  beneath  it,  which  becomes  gradually 
a  torrent  of  considerable  size,  and  finally  emerges  to  the  light 
from  beneath  the  bluff  of  ice  in  which  the  glacier  terminates. 
Thence  it  continues  on  its  rocky  course  down  the  valley. 

5.  Method  of  movement  —  The  capability  of  motion  in  a 
glacier  is  (1)  dependent  partly  on  a  degree  of  plasticity  in  ice. 
Ice  may  be  made  through  pressure  to  copy  a  seal,  or  be  drawn 
out  into  cylinders  ;  or,  if  a  slab  is  supported  only  at  the  sides, 
it  will  become  bent  downward,  through  gravity. 

13* 


298  DYNAMICAL  GEOLOGY. 

(2)  It  is  also  due  in  part  to  the  facility  with  which  ice  breaks 
and  then  becomes  united  again  into  a  solid  mass  when  the 
broken  surfaces  are  brought  into  contact.  This  quality,  first 
noticed  by  Faraday  and  applied  to  glaciers  by  Tyndall,  is 
called  re-gelation,  the  word  meaning  a  freezing  together  again. 
It  is  easily  tried  by  breaking  a  lump  of  ice  and  bringing  the 
surfaces  again  into  contact:  if  moist,  as  they  are  at  the 
ordinary  temperature,  they  at  once  become  firmly  united. 
A  glacier  moves  on  and  accommodates  itself  to  its  uneven 
bed  by  bending  or  breaking ;  and,  however  fractured,  it  may, 
when  the  movement  slackens  and  the  parts  are  pressed  to- 
gether again,  become  as  solid  as  before. 

Again  (3),  a  glacier  may  here  and  there,  at  times,  slide 
along  its  bed,  yet  only  portions  at  a  time. 

6.  Transportation  by  Glaciers.  —  Moraines.  —  Glaciers  become 
laden  with  stones  and  earth  falling  from  the  heights  above, 
or  coming  down  in  crushing  avalanches  of  snow  and  stones. 
The  stones  and  earth  make  a  band  along  either  border  of  a 
glacier,  and  such  a  band  is  called  a  moraine.  When  two 
glaciers  unite,  or  a  tributary  glacier  joins  another,  they  carry 
forward  their  bands  of  stones  with  them ;  but  those  on  the 
uniting  sides  combine  to  make  one  moraine.  A  large  glacier 
like  that  in  Fig.  401  may  have  many  moraines, —  or  one 
less  than  the  number  of  its  tributaries.  Some  of  the  masses 
of  rock  on  glaciers  are  of  immense  size.  One  is  mentioned 
containing  over  200,000  cubic  feet,  —  which  is  equivalent  in 
cubic  contents  to  a  building  100  feet  long,  50  wide,  and  40 
high. 

The  ice  also  gathers  up  masses  of  rock  from  any  hillocks 
in  the  surface  beneath  itj  easily  detaching  and  bearing  off 
great  slabs  when  the  rocks  are  jointed  or  fractured. 

In  the  lower  part  of  a  glacier  the  several  moraines  lose 
their  distinctness  through  the  melting  of  the  ice;  for  this 
brings  to  one  level  what  was  distributed  through  a  consider- 
able part  of  its  former  thickness,  and  the  surface,  therefore, 
becomes  covered  with  earth  and  stones.  The  bluff  of  ice 


GLACIERS. 


299 


which  forms  the  foot  of  a  glacier  is  often  a  dirty  mass,  show- 
ing little  of  its  real  icy  nature,  in  the  distant  view. 

The  final  melting  leaves  all  the  earth  and  stones  in 
unstratified  heaps  or  deposits,  to  be  further  transported, 
eroded,  and  arranged,  by  the  stream  that  flows  from  the 
glacier. 

7.  Erosion  by  Glaciers.  —  A  glacier  laden  with  stones  will 
have  stones  in  its  lower  surface  and  sides,  as  well  as  in  its 
mass.  As  it  moves  down  the  valley,  it  consequently  abrades 
the  exposed  rocks  over  which  it  passes,  smoothing  and  pol- 
ishing some  surfaces,  covering  others  closely  with  parallel 

Fig.  402. 


View  on  Roche-Moutonnee  Creek,  Colorado. 


scratches,  and  often  ploughing  out  broad  and  deep  channels, 
besides  scratching  and  smoothing  the  ploughing  bowlders. 

The  rocky  ledges  over  which  the  ice  has  long  moved  are 
often  reduced  to  rounded  prominences  ;  they  then  look,  in  the 


300  DYNAMICAL   GEOLOGY. 

distance,  like  groups  of  crouching  sheep,  and  hence  have 
been  called, -in  French,  roches  moutonnees.  They  are  exhibit- 
ed on  a  grand  scale  in  some  of  the  valleys  of  the  high  ranges 
along  the  summit  of  the  Rocky  Mountains,  where  were  formerly 
extensive  glaciers ;  and  Fig.  402  represents  one  of  the  scenes, 
in  the  region  of  the  "  Mountain  of  the  Holy  Cross  "  (the  re- 
moter summit  near  the  centre  of  the  view),  as  photographed 
by  the  photographer  of  the  Expedition  under  Dr.  Hayden. 
Further,  the  stones  in  the  ever-shifting  ice  wear  dne.  another, 
and  may  thereby  become  rounded  at  the  angle^f  ajad  the  very 
fine  dust  thus  made  is  carried  down  by  the  wtLfrs  along  the 
crevasses  to  make  beds  of  clay  or  earth,  and^gipe  a  milky  hue 
to  the  streams  flowing  from  a  glacier  re< 

In  addition  to  these  minor  operations,%]tojbiers  deepen  and 
widen  the  valleys  in  which  they  mof^  VBut  in  this  work 
they  are  aided  by  the  frosts  (page  »/4),  avalanches,  and 
especially  by  the  torrents  beneatk^he  glacier.  The  direct 
excavating  effects  are  small  nnllas  yfte  rocks  are  jointed  (a 
very  common  condition  even  wiYMgranite)  or  are  in  layers. 

8.  Glacier  regions.  —  The  best  VAg wn  of  Glacier  regions  are 
those  of  the  Alps,  in  one  of  whiiji  Mont  Blanc  stands,  with 
its  summit  15,760  feet  above  the  feea.  There  are  glaciers  also 
in  the  Pyrenees,  the  mountains  of  (Norway,  Spitzbergen,  Green- 
land, and  other  Arctic  regions,  in  the  Caucasus  and  Himalaya, 
in  the  Southern  Andes,  etc.  One  of  the  Spitzbergen  glaciers 
borders  the  coast  for  11  miles  with  cliffs  of  ice  100  to  400 
feet  high.  The  great  Humboldt  Glacier  of  Greenland,  north 
of  79°  20',  has  a  breadth  at  foot,  where  it  enters  the  sea,  of 
45  miles ;  and  this  is  but  one  glacier  among  many  in  that  icy 
land. 

3.  Icebergs. 

When  a  glacier,  like  those  of  Greenland,  terminates  in  the 
sea,  the  icy  foot  bearing  its  moraines  becomes  broken  off  from 
time  to  time ;  and  these  fragments  of  glaciers,  floated  away  by 
the  sea,  are  icebergs.  The  geological  effects  of  icebergs  have 
been  stated  on  page  290. 


FORMATION   OF  SEDIMENTARY   STRATA.  301 

4.    Formation  of  Sedimentary  Strata. 

The  following  is  a  brief  recapitulation  of  the  explanations 
of  the  origin  of  deposits  given  in  the  preceding  pages.  Igne- 
ous and  other  crystalline  rocks  are  not  here  included. 

1.  Sources  of  material  —  The  material  of  sedimentary  rocks, 
exclusively  of  limestones,  has  come  mainly  from  the  degrada- 
tion of  pre-existing  rocks.     But  another  part  (as  that  of  lime- 
stones, or  infusorial  earth)  has  been  taken  up  from  a  state  of 
solution  in  the  ocean  or  fresh  waters,  through  the  agency  of 
life;  yet  the  waters  have  received  the  ingredients  from  the 
rocks,  either  when  the  ocean  first  began  to  exist,  or  subse- 
quently through  the  dissolving  action  of  streams  on  exposed 
rocks. 

2.  Means  of  degradation.  —  The  principal  means  of  degrada- 
tion are  the  following :  1.  Erosion  by  moving  waters,  either 
those  of  the  sea  or  land  (pages  275,  286) ;  2.  Erosion  by  ice, 
either  that  of  glaciers,  icebergs,  or  ordinary  snow  and  ice  (page 
299) ;   3.  Pressure  of  the  water  descending  into  fissures ;  4. 
Forming  of  substances,  for  example  oxyde  of  iron,  in  cracks, 
this  tending  to  open  and  deepen  the  cracks ;  5.  Growth  of 
rootlets,  roots,  and  trunks  of'  trees,  in  crevices,  resulting  in 
opening  and  tearing  apart  rocks,  and  often  producing  exten- 
sive destruction  of  rocks,  especially  when  they  are  jointed ; 
6.  Freezing   of  water  in   fissures   (page    294) ;    7.  Chemical 
decomposition  of  one  or  more  of  the  ingredients  of  a  rock, 
in  the  course  of  which  process  the  rock  becomes  crumbled 
down  to  fragments  or  reduced  to  earth ;  8.  The  undermining 
of  rocks  by  any  method;  9.  Expansion  and  contraction  by 
heat  (page  305). 

3.  Formation  of  deposits.  —  The  principal  methods  by  which 
deposits  have  been  formed  are  the  following :  — 

7.  By  the  waters  of  the  sea.  —  1.  Through  the  sweep  of  the 
ocean  over  the  continents  when  barely  or  partly  submerged,  — 
making  (a)  sandy  or  pebbly  deposits  near  or  at  the  surface 
where  the  waves  strike,  or  at  very  shallow  depths  where 


302  DYNAMICAL   GEOLOGY. 

swept  by  a  strong  current ;  (6)  argillaceous  or  shaly  deposits 
near  or  at  the  surface,  where  sheltered  from  the  waves ;  and 
also,  at  considerable  depths,  out  of  material  washed  off  the 
land  by  the  waves  or  currents;  but  not  making  (c)  coarse 
sandy  or  pebbly  deposits  over  the  deep  bed  of  the  ocean,  as 
even  great, rivers  carry  only  silt  to  the  ocean;  and  not  mak- 
ing (d)  argillaceous  deposits  over  the  ocean's  bed  except  along 
the  borders  of  the  land,  unless  by  the  aid  of  a  river  like  the 
Amazon,  in  which  case,  still,  the  detritus  is  mostly  thrown 
back  on  the  coast  by  the  waves  and  currents. 

2.  Through  the  waves  and  currents  of  the  ocean  acting  on 
the  borders  of  the  continent ;  the  results  are  the  same  as  above, 
except  that  the  beds  so  made  have  .less  extent. 

3.  Through  living  species,  and  mainly  Mollusks,  Radiates, 
and  Khizopods,  affording  calcareous  material  for  strata,  and 
Diatoms  and  some  Protozoans,  siliceous  material.     All  rocks 
made  of  corals,  and  the  shells  of  Mollusks,  excepting  the 
smallest,  require  the  help  of  the  waves  at  least  to  fill  up  the 
interstices ;  but  Ehizopods  and  siliceous  Infusoria  may  make 
rocks  in  deep  water,  by  accumulation,  which  are  in  no  sense 
sedimentary.     See  page  265. 

2.  By  the  waters  of  lakes.  —  Lacustrine  deposits  are  essen- 
tially like  those  of  the  ocean  in  mode  of  origin,  unless  the 
lakes  are  small,  when  they  are  like  those  of  rivers. 

3.  By  the  running  waters  of  the  land.  —  1.  Filling  the  valleys 
with  alluvium,  and  moving  the   earth   from  the  hills  over 
the  plains  (page  281).     2.   Carrying  detritus  to  the  sea  or  to 
lakes,  to  make,  in  conjunction  with  the  action  of  the  sea,  or 
lake-waters,  delta  and  other  sea-shore  accumulations  (pages 
284,  290). 

4.  By  frozen  waters.  —  A.  Acting  in  the  condition  of  gla- 
ciers, and  thus  :  1.  Spreading  the  rocks  and  earth  of  the  higher 
lands  over  the  lower,  and,  in  the  process,  bearing  onward 
blocks  of  great  size,  as  well  as  finer  material  (pages  295,  298). 
2.  Distributing  rocks  and  earth  in  lines  or  moraines.  —  B. 
Acting  as  icebergs,  and,  in  this  condition,  transporting  stones 


HEAT.  303 

and  earth  to  distant  parts  of  the  ocean,  as  from  the  Arctic 
regions  to  the  Newfoundland  Banks,  and  so  contributing 
to  deep  or  shallow  water  or  shore  sedimentary  accumula- 
tions, distinguished  by  their  containing  huge  blocks  of  stone, 
besides  pebbles,  and  earth. 


IV. -HEAT. 
1.  Sources  of  Heat. 

The  crust  of  the  earth  derives  heat  from  three  sources : 
1.  The  sun,  an  external  source ;  2.  The  earth's  heated  inte- 
rior ;  3.  Chemical  and  mechanical  action. 

1.  The  sun.  —  This  agency  is  peculiar  in  being  regularly  in- 
termittent, through  the   alternations  in  the  seasons,  in  day 
and  night,  in  the  time  of  aphelion  and  perihelion,  and  in  the 
eccentricity  of  the  earth's  orbit.      The  amount  of  heat  im- 
parted to  the  earth  varies  also  with  the  density  of  the  atmos- 
phere, and  was  greater  in  early  time,  when  the  proportion  of 
carbonic  acid  and  of  moisture  was  greater  than  now. 

2.  Internal  heat  —  The  fact  of  a  high  heat  in  the  earth's  in- 
terior is  established  in  various  ways. 

1.  The  form  of  the  earth  is  a  spheroid,  and  a  spheroid  of 
just  the  shape  that  would  have  resulted  from  the  earth's  rev- 
olution on  its  axis,  provided  it  had  passed  through  a  state  of 
complete  fusion,  and  had   slowly  cooled   over  its   exterior. 
Hence  follows  the  conclusion  that  it  has  passed  through  such 
a  state  of  fusion,  which  is  greatly  strengthened  by  the  other 
evidence  here  given.   Another  conclusion  also  follows :  namely, 
that  the  earth's  axis  had  the  same  position  (or,  at  least,  very 
nearly  the  same)  when  cooling  began  as  now.     There  is  no 
evidence  that  there  has  been  at  any  time  a  change. 

2.  In  deep  borings  for  water,  like  those  mentioned  on  page 
285,  it  has  been  found  that  the  temperature  of  the  earth's 
crust  increases,  on  an  average,  one  degree  of  Fahrenheit  for 
every  50  or  60  feet  of  descent.     The  rate  of  1°  F.  for  50  feet 


304  DYNAMICAL   GEOLOGY. 

of  descent,  in  the  latitude  of  New  York,  would  give  heat 
enough  to  boil  water  at  a  depth  of  8,100  feet ;  and  at  a  depth 
of  about  28  miles  the  temperature  would  be  3000°  F.,  or  that 
of  the  fusing-point  of  iron.  Since,  however,  the  fusing  tem- 
perature of  any  substance  increases  with  the  pressure,  the 
depth  required  before  a  material  like  iron  would  be  found  in 
a  melted  state  would  be  much  greater  than  this.  More- 
over, the  ratio  of  increase  downward,  according  to  physicists, 
cannot  be  a  simple  geometrical  ratio.  Still,  the  facts  suffice  to 
prove  that  the  earth  has  a  source  of  heat  within,  and  that  a 
high  heat  exists  at  no  great  depth. 

3.  The  great  Pacific  Ocean  has  nearly  a  complete  girt  of 
volcanoes,  extinct  or  active,  and  all  of  its  many  islands  that 
are  not  coral  are  wholly  volcanic  islands,  —  excepting  New 
Zealand  and  a  few  others  of  large  size  in  its  southwest  cor- 
ner.    Volcanoes  occur  along  many  parts  of  the  Andes  from 
Tierra   del   Fuego   to   the   Isthmus   of    Darien,   in   Central 
America,  in  Mexico,  California,  Oregon,  and  beyond ;  in  the 
Aleutian  Islands  on  the  north ;  in  Kamtchatka,  Japan,  the 
Phillipines,  New  Guinea,  New  Hebrides,  and  New  Zealand  on 
the  west ;  and  on  Antarctic  lands  both  south  of  New  Zealand 
and  South  America.     The  volcanic  region  thus  bounded  is 
equal  to  a  whole  hemisphere,  and  is  ample  proof  as  to  the 
nature  of  the  whole  globe.    With  outlets  of  fire  so  extensively 
distributed  over  the  vast  area,  there  surely  must  be,  or  must 
formerly  have  been,  some  universal  seat  of  fire  beneath. 

There  are  volcanoes  also  in  the  East  Indies  in  great  num- 
bers, both  extinct  and  active,  in  the  islands  of  the  Indian 
Ocean,  in  the  West  Indies,  in  the  islands  of  the  Atlantic,  and 
in  the  vicinity  of  the  Mediterranean  and  Eed  Seas. 

4.  The  flexures  which  the  earth's  crust  and  its  strata  have 
undergone  over  regions  of  continental  extent,  and  even  as 
late  as  the  Cenozoic,  indicate  that  there  have  been,  up  to  the 
middle  Cenozoic,  if  not  later,  as  great  regions  of  liquid  rock 
beneath  the  earth's  crust. 

3.   Chemical  and  Mechanical  action.  —  In  the  upturning  and 


HEAT.  305 

flexure  of  rocks  attending  mountain-making  there  have  been 
movements  on  a  grand  scale ;  and,  through  the  transformation 
of  this  motion  into  heat,  the  rocks  have  received  in  some 
cases  a  high  temperature,  sufficient  to  promote,  through  the 
moisture  present,  the  consolidation  of  rocks,  and  even  their 
crystallization  or  metamorphisrn ;  and  also,  in  the  view  of 
Mallet,  their  fusion  on  a  scale  grand  enough  to  originate  vol- 
canoes. This  is  probably  the  chief  means  by  which  the 
metamorphism  and  consolidation  of  rocks  have  been  pro- 
duced. 

2.  Effects  of  Heat. 

The  following  are  the  effects  of  heat  here  considered :  — 

1.  Expansion  and  contraction. 

2.  Igneous  action  and  results. 

3.  Metamorphism. 

4.  Formation  of  veins. 

The  heat  of  the  globe  is  also  one  of  the  causes  of  earth- 
quakes, of  change  of  level  in  the  earth's  crust,  and  of  the  ele- 
vation of  mountains :  these  subjects  are  considered  in  the 
following  chapter.  It  is  an  important  agent  also  in  all  chemi- 
cal changes. 

I.  Expansion  and  Contraction. 

Heating  is  attended  in  rocks  by  expansion,  and  cooling  by 
contraction.  Alternate  heating  and  cooling,  connected  with 
the  movements  of  the  sun,  produce  an  expansion  and  con- 
traction of  the  superficial  layer  of  rocks  which  often  cause  it 
to  peel  off.  The  same  agency  may  gradually  move  loosened 
rocks  from  their  places. 

Again :  where  heat  from  any  subterranean  source,  or  from 
subterranean  movements,  slowly  penetrates  rocks,  it  causes 
their  expansion.  Lyell  has  calculated  that  a  mass  of  sand- 
stone a  mile  thick,  raised  in  temperature  to  1000°  F.,  would 
have  its  upper  surface  elevated  50  feet. 

Extensive  fractures  of  the  rocks  undergoing  change  of  tern- 


30G 


DYNAMICAL   GEOLOGY. 


perature  may  take  place,  and  also,  as  a  consequence,  earth- 
quakes, though  only  those  of  a  light  or  feeble  kind. 

Contraction  from  cooling,  whatever  the  source  of  the  heat, 
often  results  in  producing  shrinkage  cracks.  The  columnar 
structure  of  trap  is  referred  in  part  to  this  cause  on  page  35; 
and  sandstones  that  have  been  heated  and  cooled  sometimes 
have  the  same  structure,  though  less  perfectly. 

2.  Igneous  Action  and  Results. 

A.    General  Nature  of  Volcanoes  and  their  Products. 

Volcanoes  are  mountain-elevations  of  a  somewhat  conical 
form,  which  eject,  or  have  ejected  at  some  time,  streams  of 
melted  rock.  If  the  fire-mountain  has  at  present  no  active 
fires  within,  and  is  emitting  no  vapors,  it  is  said  to  be  extinct. 

Fig.  403. 


Volcanic  Cone. 


The  slope  of  the  cones  varies  greatly.  Those  made  of  ejected 
cinders  (fragments  of  lava)  have  the  steep  angle  in  Fig.  403. 
Etna,  about  10,000  feet  high,  and  Mount  Kea  and  Mount  Loa 
of  Hawaii,  nearly  14,000  feet,  consisting  mainly  of  lava 


HEAT.  —  VOLCANOES. 


307 


streams,  have  an  average  slope  of  less  than  10  degrees.  The 
form  of  a  cone  with  a  slope  of  7  degrees  —  which  is  the  aver- 
age for  the  Hawaian  volcanoes  —  is  shown  in  Figs.  404,  405  ; 
Fig.  404  has  a  pointed  top,  like  Mount  Kea,  and  Fig.  405 
a  rounded  outline,  like  Mount  Loa,  whose  form  is  that  of  a 
very  low  dome. 

Fig.  404. 


B 

Mount  Kea. 

Fig.  405. 


AiOUllt  1 ,0u. 

The  highest  of  volcanic  mountains  on  the  globe  are  the 
Aconcagua  peak  in  Chili,  23,000  feet,  and  Sorata  and  Illi- 
mani,  in  Bolivia,  each  over  24,000  feet.  The  former  appears 
to  be  still  emitting  vapors,  showing  that  the  fires  are  not 
wholly  extinct.  The  mountains  Shasta,  Hood,  St.  Helen's,  and 
others  in  California  and  Oregon,  are  isolated  volcanic  cones 
11,000  to  14,400  feet  high,  the  last  being  the  height  of  Mount 
Shasta.  The  average  slope  of  the  upper  half  of  Mount  Shasta 
is  about  27°.  The  slopes  of  most  of  the  lofty  volcanoes  of  the 
Andes  is  between  25°  and  32°. 

The  cavity  or  pit  in  the  top  of  a  volcanic  mountain,  where 
the  lavas  may  often  be  seen  in  fusion,  is  called  the  crater. 
It  is  sometimes  thousands  of  feet  deep,  but  may  be  quite 
shallow ;  and  in  extinct  volcanoes  it  is  often  wholly  wanting, 
owing  to  its  having  been  left  filled  when  the  fires  went  out. 

The  liquid  rock  issuing  from  a  crater,  and  the  same  after 
becoming  cold  and  solid,  is  called  lava. 

An  active  crater,  even  in  its  most  quiet  state,  emits  vapors. 
These  vapors  are  mostly  simple  steam,  or  aqueous  vapor ;  but 
in  addition  there  are  usually  sulphur  gases,  and  sometimes 
carbonic  acid  and  muriatic  acid. 

In   a   time   of   special   activity  fiery  jets    are    sometimes 


308  DYNAMICAL   GEOLOOY. 

thrown  up  to  a  great  height,  which,  in  the  distance,  at  night 
look  like  a  discharge  of  sparks  from  a  furnace.  These  jets 
are  made  of  red-hot  fragments  of  the  liquid  lava;  the  frag- 
ments cool  as  they  descend  about  the  sides  of  the  crater,  and 
are  then  called  cinders. 

When  a  shower  of  rain,  or  of  moisture  from  the  condensed 
steam,  accompanies  the  fall  of  the  cinders,  the  result  is  a 
mud-like  mass,  which  dries  and  becomes  a  brownish  or  yel- 
lowish-brown layer  or  stratum,  called  tufa.  Tufa  is  often 
much  like  a  soft  coarse  sandstone,  except  that  the  materials 
are  of  volcanic  origin. 

The  materials  produced  by  the  volcano  are,  then —  1.  La- 
vas ;  2.  Cinders;  3.  Tufas;  4.  J^apors  or  Gases,  which  are 
mostly  vapor  of  water,  partly  sulphur  gases,  and  in  some  cases 
also  carbonic  acid,  muriatic  acid,  and  some  other  materials. 

The  lavas  are  of  various  kinds.  They  are  more  or  less  cel- 
lular ;  sometimes  light  cellular,  like  the  scoria  of  a  furnace ; 
but  more  commonly  heavy  rocks  with  some  scattered  ragged 
cellules  or  cavities  through  the  mass.  A  stream  of  lava,  of 
this  more  solid  kind,  in  a  crater,  has  often  a  few  inches  of 
scoria  at  top,  —  as  a  running  stream  of  syrup  may  have  its 
scum  or  froth.  The  most  of  the  scoria  has  this  scum-like 
origin.  Pumice  is  a  very  light  grayish  scoria,  full  of  long  and 
slender  parallel  air-cells. 

The  lavas  may  be  black  or  brownish,  and  grayish  or  green- 
ish black,  in  color,  and  very  heavy  (specific  -  gravity  above 
2.9)  ;  as  doleryte,  described  on  page  26 ;  or  they  may  be 
rather  light  (specific  gravity  under  2.7)  and  grayish,  as  tra- 
cliyte  and  porphyry.  The  latter  are  mainly  feldspathic  kinds, 
while  the  former  or  heavier  kinds  contain,  besides  a  feldspar, 
iron-bearing  pyroxene,  and  usually  some  magnetite. 

A  volcanic  mountain  is  made  out  of  the  ejected  materials ; 
either  —  (1)  out  of  lavas  alone ;  or  (2)  of  cinders  alone ;  or  (3) 
of  tufas  alone ;  or  (4)  of  alternations  of  two  or  more  of  these 
ingredients.  As  the  centre  of  the  mountain  is  the  centre  of 
the  active  fires,  the  ejections  flow  off  or  fall  around  it,  and 


HEAT.  —  VOLCANOES. 


309 


hence  the  form  of  a  volcanic  peak  necessarily  tends  to  become 
conical. 

The  average  angle  of  slope  of  a  lava-cone  is  from  3°  to  10° ; 
of  a  tufa-cone,  15°  to  30°;  of  a  cinder-cone,  30°  to  42°;  of 
mixed  cones,  intermediate  inclinations  according  to  their  con- 
stitution. 

B.    Volcanic  Eruptions. 

The  process  of  eruption,  though  the  same  in  general  method 
in  all  volcanoes,  varies  much  in  its  phenomena.  The  funda- 
mental principles  are  well  shown  at  the  great  craters  of  Ha- 
waii, the  southeasternmost  of  the  Hawaian  (or  Sandwich) 
Islands. 

1.  Hawaian  Volcanoes.  —  7.  General  description.  —  Hawaii  is 
made  up  mainly  of  three  volcanic  mountains,  —  two,  Mount 
Loa  and  Mount  Kea,  nearly  14,000  feet  high ;  and  one  (the 
western),  Mount  Hualalai,  about  10,000  feet.  Mount  Kea  is 


Map  of  part  of  Hawaii. 


alone  in  being  extinct.  The  average  slopes  of  the  two  high- 
est are  shown  in  Figs.  404,  405,  on  page  307,  Fig.  404  repre- 
senting Mount  Kea  and  405  Mount  Loa. 


310  DYNAMICAL   GEOLOGY. 

Mount  Loa  has  a  great  crater  at  top,  and  another  4,000  feet 
above  the  level  of  the  sea  (at  K,  Fig.  406).  The  latter  is  the 
famous  one  called  Kilauea,  and  also  Lua  PeU  or  Pelt's  pit, 
Pele  being,  in  the  mythology  of  the  Hawaians,  the  goddess  of 
the  volcano. 

The  accompanying  map,  of  the  southeastern  portion  of  Ha- 
waii, Fig.  406,  shows  the  positions  of  Mount  Loa  and  Mount 
Kea,  and  of  the  crater  of  Kilauea,  besides  other  craters  at  the 
summit  of  Mount  Loa,  and  on  the  sides,  at  P,  A,  B,  C,  K,  etc. 

2.  Kilauea.  —  The  crater  of  Kilauea  is  literally  a  pit.     It  is 
three  miles  in  greatest   length,  and  nearly  two  in  greatest 
breadth,  and  about  seven  and  a  half  miles  in  circuit.     It  is 
large  enough  to  contain  Boston  proper  to  South  Bridge,  three 
times  over,  or  to  accommodate  400  such  structures  as  St.  Pe- 
ter's at  Rome.     The  pit  has  nearly  vertical  sides  of  solid  rock 
(made  of  lavas  piled  up  in  successive  layers),  and  has  been 
1,000  feet  in  depth  after  several  of  its  eruptions,  and  500  to 
600  when  most  filled  with  lavas.     The  bottom  is  a  great  area 
of  solid  lava ;  it  may  be  surveyed  from  the  brink  of  the  pit, 
even  when  in  most  violent  action,  as  calmly  and  safely  as 
if  the  landscape  were  one  of  houses  and  gardens.     In  some 
parts  of  it  there  are  ordinarily  one  or  more  lakes  or  pools  of 
liquid  lava,  and  from  these  and  other  points  vapors  rise.     The 
largest  lake  is  sometimes  1,000  feet  or  more  in  diameter. 

3.  Action  in  Kilauea.  —  The  ordinary  action  is  simply  this. 
The  lavas  in  the  active  pools  are  in  a  state  of  ebullition,  jets 
rising  and  falling  as  in  a  pot  of  boiling  water,  with  this  dif- 
ference, that  the  jets  are  30  or  40  feet  high.     Such  jets,  in 
lava  as  well  as  water,  arise  from  the  effort  of  vapors  to  escape ; 
in  water  the  vapor  is  steam  derived  from  the  water  itself; 
in  lavas  it  is  chiefly  steam  from  waters  that  have  gained 
access  to  the  fires,  but  with  the  aid  of  gases  derived  from 
materials  in  the  lavas. 

The  lavas  of  the  pools  or  lakes  overflow  at  times  and  spread 
in  streams  across  the  great  plain  that  forms  the  bottom  of  the 
crater.  In  times  of  great  activity  the  pools  and  lakes  are 


HEAT.  —  VOLCANOES.  311 

numerous,  the  ebullition  incessant,  the  jets  higher,  and  the 
overflowings  follow  one  another  in  quick  succession. 

4.  Cause  of  eruption.  —  By  these  overflows  the  pit  slowly 
fills.  In  the  course  of  a  few  years  the  bottom  has  thus  been 
raised  400  feet  or  more  above  its  lowest  level;  so  that  the 
depth  was  reduced  from  1,000  to  600  feet  or  less.  The 
addition  of  400  feet  increases  400  feet  the  height  of  the  cen- 
tral column  of  liquid  lava  of  the  crater,  and  causes  a  corre- 
sponding increase  of  pressure  against  the  sides  of  the  mountain. 
The  amount  of  this  pressure  is  at  least  two  and  a  half  times 
as  great  as  that  which  an  equal  column  of  water  would  pro- 
duce. The  mountain  should  be  strong  to  bear  it.  The  lavas 
at  such  times  may  be  in  a  state  of  violent  activity,  and  when 
so  there  is  an  addition  to  the  pressure  against  the  sides  of  the 
mountain,  arising  from  the  force  of  the  imprisoned  vapors. 

The  consequence  of  this  increase  of  pressure,  both  from  the 
lavas  and  the  augmented  vapors,  may  be,  and  has  several 
times  been,  a  breaking  of  the  sides  of  the  mountain.  One 
or  more  fractures  result,  and  out  flows  the  lava  through 
the  openings.  Thus  simple  have  been  the  eruptions. 

In  one  such  eruption  the  lavas  first  appeared  at  the  surface 
a  few  miles  below  Kilauea  (at  P,  Fig.  406,  on  page  309),  and 
then  again  at  other  points  more  remote,  A,  B,  C,  m ;  and 
finally  a  stream  began  at  n,  a  point  20  miles  from  the  sea, 
which  continued  to  the  shores  at  Nanawale.  Here,  on  en- 
countering the  waters,  the  great  flood  of  lava  was  shivered 
into  fragments,  and  the  whole  heavens  were  thick  with  an 
illuminated  cloud  of  vapors  and  cinders,  the  light  coming  from 
the  fiery  stream  below. 

This  eruption  of  Kilauea  took  place,  it  will  be  observed, 
not  over  the  sides  of  the  crater,  but  through  breaks  in  the 
mountain's  sides  below ;  and  the  pressure  of  the  column  of 
lava  within,  along  with  the  pressure  of  the  escaping  vapors, 
appear  to  have  caused  the  break.  In  all  known  eruptions 
of  Kilauea  the  process  has  been  that  described. 

5.  Summit-crater  of  Mount  Loa.  —  Eruptions  have  also  taken 


312 


DYNAMICAL   GEOLOGY. 


place  from  the  summit-crater  of  the  same  mountain  (Mount 
Loa),  or  at  a  point  nearly  14,000  feet  high  above  the  sea ;  and 
in  each  case  there  has  been,  not  an  overflow  from  the  crater, 
but  an  outflow  through  breaks  in  the  sides  of  the  mountain. 
In  1852  there  was  first  a  small  issue  of  lavas  near  the  sum- 
mit, and  then  another  of  great  magnitude  about  10,000  feet 
above  the  sea-level.  At  this  second  outbreak  the  lava  was 
thrown  up  in  a  fountain,  or  mass  of  jets,  several  hundred  feet 
high  ;  and  thus  it  continued  in  action  for  several  days.  The 

Fig.  407. 


156° 


20° 


155° 


ISLAND  OF  HAWAII  —  L,  Mount  Loa ;  K,  Mount  Kea ;  H,  Iftmnt  Hualalai ;  P,  Kila- 
uea  or  Lua-Pele ;  1,  Eruption  of  1843 ;  2,  of  1852 ;  3,  of  1855  ;  4,  of  1859 ;  a,  Wainiea  ;  b, 
Kawaihae  ;  c,  Wainanalii ;  d,  Kaliua ;  e,  Kealakekua ;  /,  Kaulanamauna  ;  g,  Kailiki ;  h, 
Waiohinu ;  i,  Honuapo ;  j,  Kapoho ;  k,  Nanawale ;  I,  Waipio ;  m,  first  appearance  of 
eruption  of  1868  ;  n,  Kahuku.  The  course  of  the  currents,  1,  2,  3,  and  5,  are  from  a  map 
by  T.  Coan,  and  4,  from  one  by  A.  F.  Judd. 

forms  of  the  fountain  of  liquid  fire  were  compared  by  Eev. 
Mr.  Coan  to  the  clustered  spires  of  a  Gothic  cathedral.  Similar 
lava  fountains  have  been  observed  also  at  other  eruptions  of 
the  volcano. 


HEAT.  —VOLCANOES.  313 

The  pressure  producing  the  jet  in  the  case  above  mentioned 
was  that  of  the  column  of  lava  between  the  point  of  outbreak 
and  the  level  of  the  lavas  in  the  summit-crater,  3,000  to  4,000 
feet  above.  The  same  pressure  in  connection  with  confined  va- 
pors must  have  caused  the  breaking  of  the  mountain  in  which 
the  eruption  began.  Usually,  no  great  earthquakes  accompany 
the  Hawaian  eruptions,  sometimes  not  even  slight  ones,  the 
first  announcement  being  merely  "  a  light  on  the  mountain." 
Moreover,  when  the  summit-crater  has  been  thus  active, 
Kilauea,  though  10,000  feet  lower  on  the  same  mountain  and 
even  a  larger  pit-crater,  commonly  shows  no  agitation,  no  signs 
whatever  of  sympathy. 

The  black  bands  descending  from  the  summit-crater,  on  the 
map,  Fig.  407,  show  the  courses  of  four  great  outflows  of 
lava.  The  scale  of  the  map  is  38  miles  to  the  inch. 

6.  Conclusions.  —  These  cases  of  eruption  indicate  (1)  that 
the  lavas  go  on  gradually  increasing  the  pressure  in  the  in- 
terior by  their  accumulation,  while  augmented  activity  in  the 
production  of  vapors  increases  still  further  the  pressure ;  and 
that  finally  the  mountain,  when  it  can  no  longer  resist  the 
forces  within,  somewhere  breaks  and  lets  the  heavy  liquid 
out.  They  show  (2)  that  while  earthquakes  may  attend  vol- 
canic action,  they  are  no  necessary  pait  of  it.  They  show  (3) 
that  lavas  may  be  so  very  liquid  that  no  cinders  are  formed 
during  a  great  eruption  ;  for  in  the  ebullition  of  the  lava  in 
the  boiling  lakes  of  Kilauea,  the  jets  (made  by  the  confined 
vapors)  are  thrown  only  to  a  height  of  30  or  40  feet ;  and  on 
falling  back,  the  material  is  still  hot  and  does  not  become 
cooled  fragments ;  it  either  falls  back  into  the  pool  or  lake,  or 
becomes  plastered  to  its  sides. 

At  some  of  the  eruptions  of  Mount  Loa  the  lava  has  con- 
tinued down  the  mountain  to  a  distance  of  30  or  40  miles. 

2.  Vesuvius.  —  Vesuvius  is  an  example  of  another  type  of 
volcano.  The  lavas  are  so  dense  or  viscid  that  jets  cannot 
rise  freely  over  the  surface :  the  vapors  are  therefore  kept 
confined  until  they  form  a  bubble  of  great  dimensions ;  and 

14 


314  DYNAMICAL   GEOLOGY. 

when  such  a  bubble,  or  a  collection  of  them,  bursts,  the  frag- 
ments are  sometimes  thrown  thousands  of  feet  in  height.  The 
crater,  at  a  time  of  eruption,  is  a  scene  of  violent  activity, 
and  cannot  be  approached.  Destructive  earthquakes  often 
attend  the  eruptions. 

The  lavas  at  Vesuvius  may  flow  directly  from  the  top  of 
the  crater ;  but  they  generally  escape  partly,  if  not  entirely, 
through  fissures  in  the  sides  of  the  mountain. 

3.  Comparison  of  Mount  Loa  and  Vesuvius  as  to  causes  of 
eruption  and  nature  of  the  mountains.  —  Of  the  two  causes  of 
eruption,  —  hydrostatic  pressure  and  elastic  force  of  confined 
vapors,  —  the  latter  may  be  the  most  effective  at  Vesuvius, 
while  the  former  is  so  at  Hawaii.     Mount  Loa,  on  Hawaii,  is 
an  example  of  the  great  free-flowing  volcanoes  of  the  world, 
and  the  mountain  is  almost  wholly  a  lava-cone.     Vesuvius  is 
an  example  of  a  smaller  vent  with  less  liquid  lavas ;  and  the 
cone  is  made  up  of  both  solid  lavas  and  cinders.     The  activity 
in  Mount  Loa  appears  to  be  kept  up  mainly  by  the  fresh 
waters   (rains)    which   fall  over  the  mountain  and  descend 
through  the  rocks  to  the  fires  ;  while  Vesuvius  is  in  part,  a*t 
least,  supplied  by  salt  waters  from  the  Mediterranean,  as  is 
proved  by  the  muriatic  acid  in  its  vapors,  and  the  chlorides 
among  its  saline  incrustations.     The  waters  of  any  subter- 
ranean streams  cannot  be  driven  back  by  the  lavas,  owing  to 
the  pressure  above,  and  hence  they  must  enter  and  be  taken 
up  by  the  lavas. 

4.  Lateral  cones  of  volcanoes.  —  In  eruptions  through  fissures 
the   lavas   may  continue   issuing   for   some   days  or  weeks 
through  the  more  open  or  widest  part  of  the  fissure,  and  con- 
sequently form  at  this  point  a  cone  of  cinders  or  lavas.     Thus 
have  originated  innumerable  cones  on  the  slopes  of  Etna  and 
other  volcanic  mountains. 

5.  Submarine  eruptions.  —  Eruptions  may  sometimes  take 
place  from  the  submarine  slopes  of  the  mountain  when  it  is 
situated  near  the  sea,  as  has  happened  with  Etna  and  Mount 
Loa ;  and  in  such  cases  cones  of  tufa,  or  of  solid  lavas,  may 


HEAT.— VOLCANOES;  315 

form  under  water  about  the  opened  vent.  Fishes  and  other 
marine  animals  are  usually  destroyed  in  great  numbers  by 
such  submarine  eruptions. 

6.  Subsidences  of  volcanic  regions.  —  Overwhelming  of  cities. 
—  Among  the  attendant  effects  of  volcanoes  are  the  sinking 
of  regions  in  their  vicinity  that  have  been  undermined  by 
the  outflow  of  the  lavas ;  the  tumbling  in  of  the  summit  of 
a  mountain ;  and  earthquakes,  or  vibrations  of  the  rocks  and 
also  of  the  air,  in  consequence  of  fractures.  Another  is  the 
burial,  not  only  of  fields  and  forests,  but  even  of  cities  and 
their  inhabitants,  by  the  outflowing  streams,  or  by  the  falling 
cinders  and  accumulating  tufas.  Pompeii  and  Herculaneum 
are  two  of  the  cities  that  have  been  buried  by  Vesuvius ;  and 
every  few  years  we  hear  of  some  new  devastations  of  habita- 
tions or  farms  by  this  uneasy  volcano. 

C.    Subdordinate  Volcanic  Phenomena. 

1.  Solfataras.  —  In  the  vicinity  of  volcanoes,  and  sometimes 
in  regions  in  which  no  volcanoes  exist,  there  are  areas  where 
steam,  sulphur  vapors,  and  perhaps  carbonic  acid  and  other 
gases,  are  constantly  escaping.  Such  areas  are  called  sol- 
fataras.  The  sulphur  gases  deposit  sulphur  in  crystals  or 
incrustations  about  the  fumaroles  (as  the  steam -holes  are 
called) ;  and  alum  and  gypsum  often  form  from  the  action 
of  sulphuric  acid  (another  result  from  the  sulphur  gases)  on 
the  rocks. 

Hot  springs.  —  Geysers.  —  Fountains  or  springs  of  hot  waters 
are  common  in  places  of  this  kind,  and  are  often  so  abundant 
as  to  be  used  for  baths.  Such  springs  occur  also  in  many 
other  parts  of  the  world,  especially  in  regions  of  upturned  or 
of  eruptive  rocks.  In  some  cases  the  heat  is  produced  by 
chemical  changes  in  progress  beneath ;  but  often  the  source 
is  the  same  as  for  volcanic  heat. 

When  the  heated  waters  are  thrown  out  in  intermittent  jets 
they  are  called  geysers.  The  Yellowstone  Park  in  the  Eocky 
Mountains  (between  the  parallels  of  44°  and  45°  N.,  and  the 


31G  DYNAMICAL  GEOLOGY. 

meridians  of  110°  and  111°  W.)  is  the  most  remarkable  region 
of  geysers  in  the  world,  fax  exceeding  that  of  Iceland.     One 

Fig.  408. 


Beehive  Geyser  in  action. 

of  the  geysers  —  the  "  Beehive  "  —  is  represented  in  action  in 


NON-VOLCANIC  IGNEOUS  ERUPTIONS.  317 

Fig.  408.  The  action  of  geysers  is  owing  (1)  to  the  access  of 
subterranean  waters  to  hot  rocks,  producing  steam,  which  seeks 
exit  by  conduits  upward;  (2)  to  cooler  superficial  waters 
descending  those  conduits  to  where  the  steam  prevents  farther 
descent,  and  gradually  accumulating  until  the  conduit  is  filled 
to  the  top ;  (3)  to  the  heating  of  these  upper  waters  by  the 
steam  from  below  to  near  the  boiling  point;  when  (4)  the 
lower  portion  of  these  upper  waters  becomes  converted  into 
steam,  and  the  jet  of  water  —  or  the  eruption  —  ensues. 

Heated  waters  act  on  the  rocks  with  which  they  are  in  con- 
tact and  decompose  them;  and  thus  they  become  slightly 
alkaline,  and  also  siliceous,  solutions.  The  silica  thus  taken 
into  solution  is  deposited  again  around  the  geysers  in  many 
beautiful  forms,  besides  making  the  bowl  of  the  cavity  or  basin 
from  which  the  waters  are  thrown  out,  and  forming  numerous 
petrifactions. 

When  the  basin  of  a  boiling  pool  consists  of  earth  or  mud, 
mud-cones  are  formed,  as  in  some  parts  of  the  Yellowstone 
Park,  and  also  at  Geyser  Canon  (a  branch  from  Pluton 
Canon),  north  of  San  Francisco,  California. 

Besides  hot  springs  that  deposit  silica,  there  are  others  that 
deposit  carbonate  of  lime,  making  thus  the  kind  of  porous 
limestone  called  travertine,  as  on  Gardiner's  Eiver,  Yellow- 
stone Park.  In  some  cases  the  action  of  the  waters  on  the 
rocks  exposed  to  them  gives  origin  to  different  minerals. 

D.    Igneous  Eruptions  not  Volcanic. 

It  has  been  stated  that  eruptions  of  volcanoes  generally 
take  place  through  fissures.  Fissure-eruptions  have  also  oc- 
cured  in  regions  remote  from  volcanoes.  Such  fractures  of 
the  crust  of  the  earth  must  have  descended  to  some  seat  of 
fires  or  liquid  rock.  Whatever  cause  was  sufficient  to  break 
through  to  the  fire-region  below  would  have  sufficed  to  press 
out  the  liquid  rock  from  beneath.  The  narrow  mass  of  igneous 
rock  which  fills  such  fissures  is  called  a  dike  (page  30).  The 
liquid  rock  has  sometimes  merely  filled  the  fracture,  without 


318  DYNAMICAL   GEOLOGY. 

overflowing ;  but  in  other  cases  it  has  spread  widely  over  the 
surface,  making  strata  of  great  extent  and  thickness.  The 
outflow  of  liquid  rock  has  often  been  followed  by  sedimentary 
deposits  over  the  region,  and  then  another  outflow  has  taken 
place ;  thus  making  alternations  of  fire-made  and  water-made 
strata.  The  lava  floods  of  Oregon,  Nevada,  and  Northern 
California,  although  connected  partly  with  the  volcanoes  of 
the  Cascade  Eange,  have  come  from  fissures;  according  to 
Le  Conte,  their  whole  area  is  not  less  than  200,000  square 
miles,  and  the  maximum  thickness  is  over  3,500  feet,  the 
average  being  probably  2,000  feet. 

The  igneous  rock  of  a  dike  is  very  often  without  cellules 
or  air-cavities ;  and,  if  any  are  present,  they  are  in  general 
neatly  formed,  instead  of  being  ragged  like  those  of  lavas ; 
and  such  a  rock,  having  the  cavities  filled  with  minerals  (as 
quartz,  calcite,  zeolites,  etc.),  is  called  an  amygdaloid. 

The  most  common  rocks  of  such  dikes  are  doleryte  (often 
called  trap)  (page  26),  and  peridotyte  ;  the  latter  is  a  doleryte 
containing  chrysolite.  Both  are  sometimes  called  basalt  when 
not  granular  in  texture.  Diabasyte  is  a  doleryte  containing 
chlorite,  a  hydrous  mineral  produced  during  the  process  of 
eruption  (page  326). 

Dikes  of  rocks  of  this  kind  are  mentioned  and  described  on 
page  160  as  occurring  in  various  parts  of  the  Eastern  border 
region  of  North  America.  They  constitute  the  Palisades  on 
the  Hudson ;  Bergen  Hill  and  other  heights  in  New  Jersey ; 
many  bold  bluffs  in  Connecticut  between  New  Haven  and  its 
northern  boundary;  Mount  Tom  and  Mount  Holyoke  and 
other  elevations  in  Central  Massachusetts;  ridges  in  Nova 
Scotia  near  the  Bay  of  Fundy.  '  They  are  also  common  about 
Lake  Superior,  and  over  the  western  slope  of  the  Rocky 
Mountains.  The  rocks  of  the  Salisbury  Craigs  near  Edinburgh, 
and  of  the  Giants'  Causeway  and  Fingal's  Cave,  are  other  ex- 
amples. They  are  common  on  all  the  continents,  especially  in 
the  regions  between  the  summits  of  the  border  mountains  and 
the  ocean,  which  are  usually  between  300  and  700  miles  in 


METAMORPHISM.  319 

breadth ;  as,  for  example,  between  the  Appalachians  and  the 
Atlantic,  and  between  the  Rocky  Mountains  and  the  Pacific. 

These  igneous  rocks  are  often  columnar  in  their  forms,  as 
illustrated  in  the  following  sketch  (Fig.  409)  of  a  scene  in 
New  South  Wales.  The  Giant's  Causeway  is  remarkable  for 
the  regularity  of  its  columns.  Similar  scenes  of  great  beauty 
occur  on  Lake  Superior,  and  along  the  upper  portion  of  the 


Figs.  409. 


Basaltic  columms,  coast  of  Illawarra,  New  South  Wales. 

Columbia  River,  Oregon.  These  columns  were  formed  when 
the  rock  cooled,  and  are  due  partly  to  contraction  and  partly 
to  a  concretionary  structure  produced  in  the  process  of  cool- 
ing. The  size  of  the  concretions  in  such  a  case  determines 
the  diameter  of  the  columns,  and  depends  on  the  amount  of 
material  and  the  rate  of  cooling,  the  size  being  larger  the 
slower  the  rate. 

3.   Metamorphism. 

1.  Nature  of  metamorphism.  —  The  term  metamorphism  sig- 
nifies change  or  alteration;  and,  in  Geology,  a  change  in  the 
earth's  rocks  or  strata  under  the  influence  of  heat  below  fu- 
sion, resulting  in  crystallization,  or,  at  least,  firm  solidification  : 
as  wrhen  argillaceous  shale  is  altered  to  roofing-slate,  mica- 
schist,  or  gneiss ;  argillaceous  sandstone,  to  gneiss  or  granite ; 
common  compact  limestone,  to  granular  limestone  or  statuary 
marble;  a  common  siliceous  sandstone,  to  a  hard  grit  or  to 


320  DYNAMICAL  GEOLOGY. 

quartzyie.  The  more  common  kinds  of  rocks  resulting  through 
metamorphism  are  described  on  pages  23,  24. 

2.  Effects.  —  The  effects  of  metamorphism  include  not  only 
(1)  solidification  and  (2)  crystallization,  but  also  — 

(3.)  A  change  of  color ;  as  the  gray  and  black  of  common 
limestone  to  the  white  color  or  the  clouded  shadings  of  mar- 
ble ;  and  the  brown  and  yellowish-brown  of  some  sandstones 
colored  by  iron,  to  red,  making  red  sandstone  and  jasper-rock. 

(4.)  In  most  cases,* a  partial  or  complete  expulsion  of  water, 
but  not  in  all;  for  serpentine,  a  metamorphic  rock,  is  one 
eighth  (or  13  per  cent)  water. 

(5.)  A  partial  or  complete  loss  of  bitumen,  if  this  ingredient 
be  present ;  as  when  'bituminous  coal  is  changed  to  anthracite 
or  graphite  (pages  76,  155). 

(6.)  An  obliteration  of  all  fossils;  or  of  nearly  all  if  the 
metamorphism  is  partial. 

(7.)  In  many  cases,  a  change  of  constitution ;  for  the  ingre- 
dients subjected  to  the  metamorphic  process  often  enter  into 
new  combinations :  as  when  a  limestone,  with  its  impurities 
of  clay,  sand,  phosphates,  and  fluorids,  gives  rise  under  the 
action  of  heat  not  merely  to  white  granular  limestone,  but  to 
various  crystalline  minerals  disseminated  through  it,  such  as 
mica,  feldspar,  scapolite,  pyroxene,  etc. 

(8.)  Often  only  a  change  in  crystallization  with  little  in 
chemical  constitution ;  as  when  a  limestone  is  turned  to  white 
statuary  marble ;  and  a  sandstone  or  argillaceous  rock,  made 
from  the  granulation  of  granite,  gneiss,  and  related  rocks,  is 
changed  to  granite  or  gneiss  again. 

It  is  thus  seen  that  metamorphism  may  fill  a  rock  with 
crystals  of  various  minerals.  Even  the  gems  are  among  its 
results ;  for  topaz,  sapphire,  emerald,  and  diamond  have  been 
produced  through  metamorphic  action.  What  is  of  more 
value,  this  process  makes  out  of  rude  shales  and  sandstones 
hard  and  beautiful  crystalline  rocks,  as  granite  and  marble, 
for  architectural  and  other  purposes.  Man's  imitations  of  na- 
ture in  this  line  are  seen  in  his  little  red  bricks. 


METAMORPHISM.  321 

3.  Process.  —  Water  and  heat  are  two  agencies  essential  in 
metamorphism. 

Metamorphism  has  taken  place  generally  when  the  rocks 
were  undergoing  great  disturbances  or  uplifts,  foldings  and 
faultings,  and,  therefore,  when  the  conditions  were  favorable 
for  the  production  of  heat  (page  304).  This  heat  has  pene- 
trated everywhere  the  moist  rocks.  The  water  or  moisture 
within  the  rocks  has  rendered  them  good  conductors  of  heat, 
and  has  aided  directly  in  conveying  the  heat.  Moreover, 
where  the  heat  was  above  212°  F.,  or  the  boiling-point  of 
water,  —  as  it  probably  has  been  in  most  cases  of  metamor- 
phic  change,  —  all  of  it  has  passed  to  what  is  called  a  super- 
heated state ;  and  in  this  state  it  has  great  power  in  dissolving 
and  decomposing  minerals  and  promoting  new  combinations 
and  crystallizations.  Under  such  circumstances,  the  moisture 
becomes  itself  a  solution  by  taking  up  mineral  substances 
from  the  rock  in  which  it  is  at  the  time ;  and  these  added 
materials  are  the  source  of  a  large  part  of  its  power  in  making 
changes ;  for  if  it  thus  becomes  an  alkaline  siliceous  solution, 
like  the  waters  of  the  Geysers  (see  page  316),  it  may  not 
only  deposit  quartz  in  all  seams  or  cavities,  if  the  tempera- 
ture favors  this,  but  it  may,  under  other  favorable  circum- 
stances, help  in  making  feldspars,  micas,  and  other  alkaline 
siliceous  minerals ;  or,  if  the  alkalies  are  mostly  absent  and 
iron  is  present,  the  siliceous  waters  may  promote  the  crystal- 
lization of  staurolite  and  hornblende. 

The  change  of  a  siliceous  sandstone  to  a  grit  or  quartzyte 
requires  nothing  but  these  conditions ;  for  the  moisture  in 
such  a  rock  would  become,  when  subjected  to  slow  heating, 
siliceous,  from  the  material  of  the  sandstone,  and  the  silica 
taken  up  would  be  deposited  again  as  the  rock  cooled,  and  so 
cement  and  solidify  the  whole  into  quartzyte.  Such  quartzytes 
generally  contain  at  least  traces  of  feldspar,  enough  to  afford 
the  alkali  requisite  to  enable  the  waters  to  dissolve  the  silica. 

These  are  examples  of  the  various  ways  in  which  heated 
and  superheated  waters  may  aid  in  metamorphic  changes. 

14*  U 


322  DYNAMICAL  GEOLOGY. 

Direct  experiments  have  shown  that  these  kinds  of  crystalli- 
zations do  result  from  the  action  of  heat. 

Pressure  is  requisite  for  most  metamorphic  changes.  Lime- 
stone heated  without  pressure  loses  its  carbonic  acid  and  be- 
comes quick-lime,  as  in  a  lime-kiln;  but  if  under  pressure, 
the  carbonic  acid  is  not  driven  off.  The  possibility  of  the 
crystallization  of  limestone  by  heat,  under  pressure,  has  been 
proved  by  direct  experiment.  The  necessary  pressure  may 
be  that  of  an  ocean  above ;  but  it  may  as  well  be  that  of  the 
superincumbent  rocks,  a  few  hundred  feet  of  which  would  be 
quite  sufficient. 

The  similarity  of  argillaceous  sandstones  to  gneiss  or  gran- 
ite is  often  much  greater  than  appears  to  the  eye.  They  have 
been  made  by  the  wear  of  just  such  rocks  as  gneiss  and  gran- 
ite ;  and  the  quartz  of  the  former  is  the  quartz  of  the  latter, 
the  clay  of  the  former  frequently  only  the  pulverized  feldspar 
of  the  latter,  and  mica  may  be  in  grains  in  the  former  as  it  is 
in  the  latter:  so  that  the  change  would  in  such  a  case  be 
mainly  a  change  in  the  state  of  crystallization.  By  heating  a 
bar  of  steel  to  a  temperature  far  short  of  fusion,  and  cooling  it 
again,  it  may  be  made  coarse  or  fine  steel,  the  process  chang- 
ing the  grains  by  causing  many  small  grains  to  combine  to 
make  the  large  ones  in  the  coarser  kind  and  the  reverse  for 
the  finer  kind.  There  is  something  analogous  in  the  change 
of  an  argillaceous  sandstone  to  a  gneiss  or  granite  above  de- 
scribed. 

Often,  however,  the  material  derived  from  the  wear  of 
gneiss  and  granite  and  other  rocks  is  not  only  pulverized, 
but  also  more  or  less  decomposed :  the  feldspar,  for  example, 
may  have  undergone  a  change  in  its  alkalies,  or  lost  them 
altogether,  they  being  carried  off  by  waters ;  or  the  mica  may 
have  lost  its  oxide  of  iron  and  alkalies  ;  or  waters  may  have 
brought  in  oxide  of  iron,  or  other  ingredients ;  and  so  on  :  and 
in  such  a  case  the  process  of  metamorphism  could  not,  of 
course,  restore  the  original  rock.  The  new  rock  made  would 
contain  no  feldspar  if  the  alkalies  had  been  removed ;  but  it 


FORMATION   OF  VEINS.'  323 

might  be  an  argillyte,  or,  if  much  oxide  of  iron  were  present, 
a  hornblende  rock,  or  some  other  kind,  according  to  the  nature 
.of  the  material  subjected  to  the  change,  the  amount  or  con- 
tinuance of  the  heat,  and  the  presence  of  much  or  little 
moisture. 

Examples  of  the  metamorphism  of  extensive  regions  of  the 
earth  have  already  been  mentioned  on  pages  75,  91,  and  these 
pages  should  here  be  perused  anew.  Local  metamorphism  has 
often  taken  place  along  the  walls  of  trap-dikes,  the  minerals 
epidote,  tourmaline,  garnet,  chlorite,  etc.,  there  at  times  oc- 
curring, being  examples  of  true  metamorphic  products.  It 
has  also  been  observed  in  the  vicinity  of  hot  springs. 

4.  Formation  of  Veins. 

1.  Nature  and  origin  of  spaces  occupied  by  veins.  —  Veins 
occupy :  (1)  the  cracks  and  fissures  made  in  rocks ;  (2)  open- 
ings between  their   layers,  especially  in  schistose  or  slaty 
kinds.     These  fissures  and  openings  are  produced  in  great 
numbers  when  a  region  of  rocks  is  undergoing  uplift,  or  when 
a  folding  of  the  strata  is  in  progress.     They  are  often  accom- 
paniments of  metamorphic  change,  the  fissures  made  becom- 
ing filled  at  the  same  time  that  the  rock  is  being  crystallized. 
The  heat  concerned  in  such  a  case  is,  as  explained  above, 
that  derived  from  the  movements  in  the  strata  in  connection 
with  that  of  the  earth's  depths.     If  fractures  reach  down  to  a 
region  of  liquid  rock  they  become  filled,  and  dikes  are  formed 
instead  of  ordinary  veins.     Some  small  fissurings  of  rocks  are 
only  the  cracks  made  by  contraction  on  cooling.     Several  fig- 
ures of  veins  are  given  on  page  30. 

2.  Origin  of  veins.  —  The  following  are  the  common  methods 
by  which  veins  have  been  made. 

7.  When  the  fissures  or  openings  were  filed  from  either  side  or 
below,  and  did  not  descend  to  regions  of  liquid  rock,  being  not 
connected  with  igneous  ejections.  —  Veins  of  this  kind  are  far 
the  most  numerous.  They  include  nearly  all  those  filled  with 
quartz  or  granite,  whether  containing  metallic  ores,  or  not, 


324  DYNAMICAL   GEOLOGY. 

and  all  banded  mineral  veins  (page  30).  The  fissures,  or 
openings,  and  part  of  the  heat  are  a  result  of  profound  disturb- 
ances such  as  give  rise  also  to  metamorphism.  The  material 
of  the  vein  is  brought  into  the  opening  from  the  rock  adjoin- 
ing, either  that  directly  adjoining,  or  that  of  depths  below. 
The  rocks  being  heated,  as  above  stated,  all  moisture  present 
tends  to  decompose  the  rock  material ;  it  takes  alkalies  from 
the  feldspars,  and  then  is  able  to  take  up  also  the  silica  and 
so  become  siliceous ;  and  if  the  heat  is  much  above  212°  F.,  or 
is  that  of  superheated  steam,  few  minerals  will  withstand  its 
action.  The  moisture,  moreover,  would  press  into  all  open- 
ings and  fill  them ;  then  its  mineral  material  sooner  or  later 
would  begin  to  be  deposited  or  crystallized ;  as  it  was  deposit- 
ed, other  mineral  matters  would  be  passed  in  to  supply  the 
place  of  that  thus  lost ;  and  so  the  current  would  be  kept  up 
until  the  supply  was  exhausted,  or  the  heat  failed,  or  the  fis- 
sure was  full.  Under  such  a  process  it  is  natural  that  veins 
in  gneiss  and  mica-schist  should  be  granitic  veins,  for  these 
rocks  contain  the  quartz,  feldspar  and  mica  of  granite ;  or  that 
they  should  often  be  quartz  veins  simply. 

Under  the  action,  whatever  metallic  ores,  or  material  of 
gems,  the  fissured  rock  contains,  is  swept  into  the  fissure 
with  the  other  mineral  material ;  and  additions  may  be  re- 
ceived largely  through  vapors  rising  from  its  deeper  parts. 

By  such  means  veins  have  been  filled  with  their  gems,  or 
with  their  ores.  The  quartz  veins  and  seams  in  the  slate 
rocks  of  a  gold  region  have  in  this  way  become  gold-bearing 
veins,  the  gold  and  quartz  having  been  brought  in  by  the 
same  moisture,  and  both  having  been  gathered  from  the  rocks 
adjoining  the  openings.  These  openings,  in  the  case  of  aurif- 
erous quartz  veins,  were  mostly  openings  between  layers  of 
the  slate  made  by  the  folding  or  upturning.  Veins  filled  by 
this  lateral  inflow  of  material,  in  connection  with  emanations 
from  the  deeper  parts  of  fissures,  would  sometimes  be  uniform 
in  material  throughout,  as  in  many  quartz  veins  or  seams ; 
but  they  might  also  consist  of  bands  of  different  materials, 


FORMATION  OF  VEINS.  325 

like  many  metallic  veins  (page  30).  In  the  formation  of  the 
latter,  the  process  has  brought  in  for  a  while  one  kind  of  min- 
eral, as  quartz,  and  deposited  it  over  the  walls  of  the  fissure ; 
then  through  some  change  some  other  mineral  or  ore,  as  an 
ore  of  lead,  or  one  of  zinc,  or  one  of  copper  ;  then  quartz  again, 
or  fluorite,  or  calcite  ;  and  so  on  until  the  vein  was  filled. 

By  such  means,  the  earth's  precious  metals  have  been  gath- 
ered out  of  the  rocks  in  which  they  were  so  sparingly  dissemi- 
nated as  to  be  of  no  service  to  art,  into  generous  veins,  and 
thereby  placed  within  reach  of  the  miner. 

2.  Where  the  fissures  descended  to  regions  of  liquid  rock  and  "were 
filled  from  below.  —  Dikes  of  porphyry,  doleryte,  and  related 
rocks  are  sometimes  the  courses  of  veins  of  metallic  ores. 
The  veins  are  generally  situated  near  the  walls  of  the  dike,  and 
either  in  the  igneous  rock  or  in  the  rock  adjoining.  The 
veins  were  made  either  when  the  dike  was  made,  or  they  oc- 
cupy fissures  made  subsequently,  but  during  the  same  epoch 
of  disturbance.  The  metallic  materials  of  the  vein  have  been 
brought  up  in  some  state  of  combination  as  solutions  or  vapors, 
either  from  the  depths  that  afforded  the  igneous  rock  itself, 
or,  more  probably,  from  the  walls  of  a  deep  part  of  the  fissure. 
The  veins  of  native  copper  at  Keweenaw  Point,  those  of  the 
same  metal  with  ores  of  copper  in  the  Red  sandstone  (Tri- 
assico-Jurassic)  of  the  Connecticut  Valley,  New  Jersey,  and 
Pennsylvania,  those  of  silver  ores  in  Nevada,  thus  originated 
in  connection  with  disturbances  accompanying  or  following 
igneous  ejections ;  the  ores  not  coming  up  in  the  fused  state 
like  the  igneous  rock,  but  mainly  through  the  aid  of  moisture, 
and  often  that  of  subterranean  waters  which  gained  access 
to  the  depths  below  when  the  fissures  were  opened. 

In  periods  of  igneous  ejections,  fissures  have  frequently 
been  made  that  have  received  not  igneous  rock,  but  only 
vapors  or  mineral  solutions  from  below,  and  thus  have  be- 
come metallic  veins.  Each  of  the  regions  just  mentioned 
contains  examples  of  such  veins. 

When  igneous  rocks  have  been  ejected  through  sedimentary 


326  DYNAMICAL   GEOLOGY. 

rocks,  and  there  were  subterranean  waters  underneath  or  be- 
tween the  sedimentary  beds,  these  waters  have  often  entered 
into  the  ascending  fiery  mass  (page  313)  and,  from  that 
level,  changed  the  character  of  the  igneous  rock,  making  in  it 
one  or  more  hydrous  minerals  (as  chlorite,  or  zeolites)  besides 
making  it  softer  and  lighter.  Thus  dolerytic  rocks  have  been 
changed  to  diabasyte,  page  26,  and  trachyte,  to  phonolyte, 
page  27.  Through  the  same  waters,  minerals  have  been 
made  out  of  the  materials  of  the  rocks  aided  by  any  mineral 
material  the  waters  carried  in  with  them,  and  thus  the  cavi- 
ties of  amygdaloids,  and  any  fissures,  have  been  filled  with 
crystallizations  of  zeolites,  and  with  agates,  etc.  Vaporizable 
or  soluble  minerals  in  the  sedimentary  beds  —  even  bitumi- 
nous substances  —  also  have  been  sometimes  carried  in  with 
the  waters  and  have  contributed  to  the  filling  of  the  cavities. 

3.  Fissures  filed  by  infiltration  or  deposition  from  above.  —  Wide 
cracks  opening  to  the  surface  have  sometimes  been  filled  with 
sand  or  earth,  producing  a  kind  of  vein  or  dike.  Small  cracks 
through  rocks  have  often  been  filled  with  calcite  (carbonate 
of  lime)  by  infiltration  from  above,  and  sometimes  by  other 
mineral  material  held  in  solution  by  infiltrating  waters. 

3.  So-called  veins  that  are  not  true  veins,  —  In  the  course 
of  the  earth's  rock-making,  metallic  ores  have  been  deposited 
along  with  the  detritus  when  a  sedimentary  bed  was  in  pro- 
gress of  formation ;  they  have  been  brought  into  marshes  by 
running  waters  from  the  decomposing  rocks  of  the  region 
around.  Deposits  of  iron  ores  are  thus  made  at  the  present 
time ;  and  in  early  geological  ages  those  of  zinc,  cobalt,  nickel, 
copper,  were  also  thus  made.  The  iron-bearing  deposits  of 
this  kind  are  most  extensive  the  farther  we  go  back  in  geo- 
logical time.  When  strata  containing  such  metalliferous 
layers  have  undergone  uplifts  and  crystallization,  the  nearly 
vertical  beds  look  like  veins.  The  cobalt  and  nickel  "  veins  " 
of  Chatham,  Connecticut,  and  the  great  iron-ore  deposits  of 
the  Archaean  terranes,  are  merely  beds,  not  veins. 

Depositions  of  ore  have  taken  place  in  cavities  in  rocks,  as 


RESULTS   OF  THE  EARTH'S   CONTRACTION.         327 

of  galenite  or  lead  ore  in  the  magnesian  limestone  of  Wiscon- 
sin and  Missouri,  and  in  the  Carboniferous  limestones  of  Der- 
byshire, England.  The  ore  region  is  often  called  a  region  of 
veins  of  ore,  when,  in  fact,  there  are  only  local  deposits. 

V.  — THE  EARTH  A  COOLING  GLOBE. 
I.  General  Considerations. 

In  the  preceding  chapters  the  origin  of  many  geological 
phenomena,  and  of  some  of  the  earth's  features,  have  been 
briefly  explained. 

A.  Changes  of  level  have  been  described  as  caused  (1)  by 
change  of  temperature,  this  cause  producing  the  expansion 
and  contraction  of  rocks  (page  305) ;  (2)  by  undermining  due 
to  subterranean  water  (page  286) ;  (3)  by  undermining  due 
to  volcanic  outflows  (page  315). 

B.  Folding  of  beds  has  been  shown  to  be  sometimes  caused, 
when  they  are  clayey,  soft,  and  wet,  by  a  lateral  movement 
produced  through  the  pressure  of  superincumbent  beds  (page 
286). 

C.  Fractures  and  faultings  of  strata  have  been  attributed  (1) 
to  undermining  by  different  methods  (pages  286,  315) ;  (2)  to 
contraction  or  expansion  on  cooling  (page  305) ;  (3)  to  the 
expansive  force  of  vapors  (page  311) ;   (4)  to  the  hydrostatic 
pressure  of  a  column  of  lava  (page  311) ;  and  to  other  causes. 

D.  Metamorphism  has   been   described  as   produced  on  a 
small   scale,  (1)  in  the  vicinity  of  dikes   of  igneous  rock, 
through  the  heat  of  the  rock  when  it  was  cooling  from  fusion 
and  (2)  sometimes  in  the  neighborhood  of  hot  springs  (page 
323). 

E.  Earthquakes  are  stated  to  result  from  fractures  of  rocks 
in  subterranean  regions,  consequent  (1)  on  undermining  (page 
286) ;  or  (2)  on  movements  and  fractures  attending  volcanic 
action  (page  314). 

But  none  of  the  causes  that  have  been  considered  explain 
the  great  changes  of  level  involving  large  parts  of  continents 


328  DYNAMICAL  GEOLOGY. 

or  of  oceanic  areas ;  or  the  flexures,  fractures,  faults,  and  up- 
lifts attending  the  making  of  mountains ;  or  the  widespread 
(or  regional)  metamorphisrn  that  has  turned  simultaneously 
sedimentary  beds  over  thousands  of  square  miles  into  crystal- 
line rocks ;  or  the  earthquakes  that  have  shaken  a  hemisphere. 

For  these  grander  phenomena  in  the  earth's  history  the 
only  explanation  is  found  in  the  fact  that  the  Earth  has  al- 
ways been,  and  still  is,  a  cooling  globe. 

That  the  earth  was  once  liquid  is  now  generally  admitted. 
If  so,  the  cooling  is  a  fact,  and  contraction,  the  attendant  of 
cooling,  is  a  necessary  consequence. 

The  earth's  interior,  —  On  the  basis  of  physical  principles, 
the  conclusion  has  been  announced  that  the  earth  is  now 
essentially  solid  throughout.  But  geology  shows  that  the 
earth's  surface  over  vast  regions  has  been  undergoing,  through 
past  time,  elevations  and  subsidences ;  and  that  these  risings 
and  sinkings  continued  on  through  the  Tertiary  age,  when 
they  were  as  great  as  in  any  preceding  age ;  and  that  even  in 
Quaternary  time  they  were  still  in  progress :  and  thus  it  de- 
monstrates that  the  crust  through  geological  history  was  not 
fastened  to  a  solid  interior;  that  either  the  interior  was  all 
liquid,  or  else  an  outer  layer  beneath  the  crust  was  liquid. 

Hopkins  has  argued  that,  in  the  process  of  solidification  from 
a  liquid  condition,  the  interior  would,  probably,  first  become 
solid,  owing  to  the  superincumbent  pressure,  —  on  the  ground 
that  pressure  would  lower  the  point  of  fusion ;  that,  later,  a 
crust  would  form  from  cooling,  leaving  for  a  time  a  liquid 
layer  between  the  crust  and  the  solid  nucleus ;  that,  ulti- 
mately, the  crust  would  become  united  to  the  nucleus  by  the 
continued  cooling.  This  condition  —  that  of  a  liquid  layer 
beneath  an  outer  crust  —  is  sufficient  to  meet  the  require- 
ments of  geological  science. 

The  force  resulting  from  contraction.  —  After  a  crust  was 
completed  around  the  sphere,  it  went  on  gradually  thicken- 
ing, from  the  continued  cooling.  Contraction  was  therefore  in 
progress  from  the  first,  and  this  contraction  would  have  pro- 


RESULTS  OF  THE  EARTH'S  CONTRACTION.        329 

duced  lateral  pressure  within  the  crust,  or  a  pressure  or  lat- 
eral thrust  of  every  part  against  the  part  adjoining.  Now,  the 
lateral  pressure  thus  occasioned  is  the  agent  that  has  pro- 
duced the  earth's  profoundest  movements  and  carried  forward 
its  development.  It  belongs  to  the  sphere  in  its  unit  capa- 
city, and  hence  it  was  adequate  to  produce  events  that  were 
comprehensive  and  universal :  and  as  cooling  still  continues, 
it  has  not  even  now  ceased  its  work. 

2.  General  Results  of  the  Lateral  Pressure. 

The  comprehensive  force  of  lateral  pressure,  working  with 
extreme  slowness,  yet  with  irresistible  power,  caused,  under 
the  conditions  stated,  — 

1.  Upward   bendings   in  the  crust,  or  geanticlinals,    and 
downward  bendings,  or  geosynclinals,  which,  even  if  exceed- 
ingly slight  deformations  of  the  sphere,  might  make  .changes 
in  the  level  of  thousands  of  feet. 

2.  Great  fractures  of  the  crust,  if  any  parts  were  weaker 
than  others,  and  shavings  of  one  face  of  the  fracture  against 
the  other,  producing  a  faulting  of  the  strata,  and  sometimes 
a  crushing  of  the  rock  by  the  friction. 

3.  Foldings  of  the  yielding  sedimentary  strata  of  the  super- 
crust, — such  as  characterize  the  Appalachians  (pages  152, 153) 
and  most  mountain  regions,  —  accompanied  by  fractures  and 
faults ;  and  also  by  crushing  on  a  vast  scale  where  the  folds 
and  fractures  are  most  numerous,  or  the  rocks  most  unyield- 
ing or  brittle. 

4.  Earthquakes  that  shake  a  continent  or  hemisphere  in 
consequence  of  the  abrupt  fracturings  or  movements  above 
referred  to ;  and  lighter  vibrations  wherever  there  was  a  slight 
yielding  to  any  strain  consequent  —  it  may  be  remotely  — 
upon  such  movements. 

5.  Compression   and   straining  of  rock    strata   over  wide 
regions,  until  they  broke  along  planes  at  right  angles  nearly  to 
the  pressure,  and  became  (1)  jointed   throughout  (page  35) ; 
or,  if  the  strata  were  clayey,  (2)  thinly  laminated  like  slate,  as 
exemplified  in  common  roofing-slate  (page  36). 


330  DYNAMICAL   GEOLOGY. 

6.  Heating  of  the  upturned,  flexed,  fractured,  faulted,  and, 
in  some  parts,  crushed  strata,  over  wide  areas,   through  the 
transformation  of  the  motion  into  heat  (page  304),  and,  thence, 
the  consolidation  and  metamorphism  of  rocks  on  a  scale  as  vast 
as  the  world's  supercrust  exemplifies. 

7.  Opening  passages,  through  the  fractures  made,  down  to 
deep-seated  subterranean  regions  of  plastic  rock ;  and  some- 
times pushing  the  mobile  rock  up  to,  and  over,  the  surface,  in 
the  form  of  igneous  eruptions,  or,  when  the  vents  remained 
permanently  open,  producing  lines  of  volcanoes, 

8.  Making  mountain-chains,  and  thereby  evolving,  in  the 
course  of  the  ages,  the  profounder  surface  features  of  the  con- 
tinents and  the  oceanic  basins. 

9.  Causing  the  smaller  changes  in  the  water-level,  over  and 
about  the  continental  areas,  either  by  movements  of  the  land 
or  of  the  ocean's  bottom,  and  thus  fixing  the  limits  to  the 
accumulating  beds  of  earthy  sediment  in  these  waters,  and  to 
the  growing  strata  of  limestones. 

10.  Changes  in  the  earth's  climate,   (1)  by  increasing   the 
height  and  extent  of  high-latitude  lands,  and  so  increasing 
cold,  —  and  the  reverse  with  tropical  lands ;  (2)  by  changes  of 
level  over  parts  of  the  continents  or  oceans  sufficient  to  change 
the  direction  of  the  great  oceanic  currents,  —  e.  g.  a  rising  of 
Arctic  lands  excluding  the  warm  currents  of  the  oceans,  and 
diminishing  the  mean   temperature  of  the  higher  northern 
latitudes  (as  in  the  Glacial  period),  or  a  sinking  giving  a  free 
admission  to  these  currents,  with  a  contrary  effect  (as  in  the 
Miocene  period). 

11.  The  formation  of  the  oceanic  basin  and  continental 
areas  or  plateaus.     This  last-mentioned  effect  was  the  first  in 
time.     It  took  place  when  the  crust  was  first  solidified,  as  is 
proved  by  the  facts  brought  out  in  early  geological  history 
(page  78).     It. was  a  necessary  consequence  of  the  compre- 
hensiveness of  the  agency  of  contraction  from  cooling,  and 
was  due,  as  the  author  has  elsewhere  explained,  to  the  con- 
tinents beini?  the  areas  which  first  became  solid.     The  oceanic 


RESULTS   OF   THE  EARTH'S   CONTRACTION.        331 

areas,  later  solidifying,  contracted  and  sunk  as  the  process 
went  forward,  so  that  a  basin  was  thus  formed,  and  one  that 
has  abrupt  slopes  toward  the  plateaus.  Thus,  when  the  crust 
was  first  completed,  it  had  its  great  depressions  begun ;  and 
the  consequences  of  this  inequality  of  the  first  surface  are 
seen  in  every  future  step  of  progress  in  the  earth's  geological 
history. 

3.  Evolution  of  the  Earth's  Fundamental  Features. 

The  prominent  facts  in  the  earth's  features  are  these  :  — 

1.  The  continents  have  mountains  along  their  borders,  and 
hence  a  basin-shaped  interior  (page  8). 

2.  The  highest  mountain-border,  and  that  consisting  of  the 
largest  number  of  independent  ranges,  faces  the  largest  ocean, 
and  conversely. 

3.  Volcanoes  about  continents  are  confined  almost  solely 
to  the  borders  of  the  oceans  or  the  border-mountains;   and 
they  are  in  great  numbers  on  all  the  sides  of  the  largest  ocean, 
the  Pacific,  and  few,  or  wanting,  on  those  of  the  smaller,  the 
Atlantic. 

4.  Foldings   of  strata    characterize   the   mountain-border 
of  a  continent,  and  only  sparingly,  where  at  all,  the  Interior 
region;  and  these  folds,  when   bold,  always  have   one   side 
steeper  than  the  other. 

5.  The  features   of  the   North  American   continent  were 
defined  in  the  first  mountain-making  of  history  >  —  that  of  the 
Archsean  (page  78) ;  and  all  ranges  of  mountains  later  made 
in  any  part  were  approximately  parallel  to  the  earlier  Archaean 
lines  of  that    part  (page  249).      Thus  the  adult  character- 
istics of  the  continent  were  as  plainly  manifested  in  its  begin- 
nings as  those  of  a  Vertebrate  in  its  embryo  stage. 

1.  Why  were  mountains  made  along  the  borders  of  the  Conti- 
nents, and  why  raised  highest  and  in  the  largest  number  of  long 
lines,  and  why  attended  by  the  mos't  and  loftiest  volcanoes,  on  the 
sides  of  the  largest  ocean?  —  The  oceanic  area,  besides  being 
depressed  much  below  the  continental,  has,  as  observed  above, 


332  DYNAMICAL  GEOLOGY. 

rather  abrupt  sides.  Hence,  while  the  lateral  pressure  in  the 
crust  was  universal  over  the  sphere,  the  force  in  the  oceanic 
crust  acted  obliquely  upward  against  the  crust  of  the  conti- 
nental border.  The  action  was  that  of  a  shove  or  thrust 
from  the  direction  of  the  ocean,  and  in  each  oceanic  area 
was  somewhat  proportional  to  the  extent  of  it ;  conse- 
quently, bendings,  uplifts,  fractures,  foldings  of  strata,  earth- 
quakes, mountain-making,  became  eminently  features  of  the 
continental  borders,  and  most  prominently  so  of  the  borders 
which  faced  the  largest  oceans. 

2.  Method  of  action,  and  its  progress  in  North  America.  —  The 
two  systems  of  forces  engaged  in  the  progress  of  North  Amer- 
ica were  those  of  the  Atlantic  and  Pacific,  —  the  latter  the 
greatest.  Under  their  action  the  V-shaped  Archaean  dry  land 
(map,  page  73)  was  first  defined,  one  branch  stretching  north- 
eastward to  Labrador  and  the  other  northwestward  to  the 
Arctic,  and  thus  facing  respectively  the  Atlantic  and  Pacific ; 
while  mountains  were  made  along  the  course  of  the  Appala- 
chian chain  and  the  Blue  and  Highland  ridges.  It  follows, 
from  the  courses  of  the  arms  of  the  V>  and  of  the  moun- 
tains, that  the  Atlantic  force  acted  mainly  from  the  south- 
eastward and  the  Pacific  from  the  southwestward,  and  the 
two,  therefore,  nearly  at  right  angles  to  one  another.  It 
is  also  apparent  that  the  Pacific  force  even  then  was  the 
greater,  and  hence  the  Pacific  Ocean  the  larger;  for  the 
northwestward  branch  of  the  V  is  far  the  longer. 

Thus  the  Archaean  nucleus  was  outlined,  and  the  position 
of  Hudson's  Bay  determined  within  the  arms  of  the  V-  From 
this  nucleal  dry  land  progress  went  forward  southeastward, 
or  toward  the  Atlantic,  and  southwestward,  or  toward  the 
Pacific,  successive  formations  being  added  under  gentle  oscil- 
lations, and  the  dry  land  gradually  extending  under  changes 
of  level  caused  mainly  by  the  same  forces.  Then,  when  the 
Lower  Silurian  closed,  appeared  the  Green  Mountains ;  and 
when  Paleozoic  time  was  closing,  appeared  the  Alleghany 
part  of  the  Appalachian  chain,  parallel  to  the  eastern  branch 


RESULTS   OF   THE   EARTH'S   CONTRACTION.        333 

of  the  Archaean  heights.  Later  still  rose  the  trap  ridges  of 
the  Mesozoic  on  the  Atlantic  border  (page  160),  making  an- 
other parallel  to  the  eastern  branch,  or  tripling  the  arm  of  the 
V  on  the  east,  and  even  repeating  all  the  bends  in  the 
Appalachians. 

Again,  on  the  Pacific  side,  other  ranges  were  made  parallel 
to  the  course  of  the  Bocky  Mountain  chain;  among  them 
after  the  Jurassic  period,  the  Sierra  Nevada,  Wahsatch,  and 
Cascade  range,  the  last  with  its  many  volcanoes,  also  Creta- 
ceous ranges,  and  still  later  Tertiary  ridges,  each  epoch  adding 
new  parallels  to  the  western  branch  of  the  Archaean  nucleus. 
Finally,  in  the  course  of  the  Tertiary,  the  mass  of  the  Rocky 
Mountains  rose  to  its  full  height  above  the  ocean. 

Each  added  range,  as  is  seen,  proves  that  the  mountain- 
making  forces  continued  to  act  to  a  large  degree  from  the  same 
directions  as  in  Archaean  time. 

The  intersection  of  the  uplifts  produced  by  the  Atlantic  and 
Pacific  forces  may  be  distinguished  over  the  interior  of  North 
America ;  for  the  courses  of  the  uplifts  of  the  Coal-formation 
in  Illinois  and  the  trend  of  Florida  are  parallel  to  the  Pacific 
border,  and  the  line  between  these  two  intersects  the  Appa- 
lachian chain  in  Eastern  Tennessee. 

Thus  the  continent  made  progress,  adding  layer  after  layer 
to  the  rocks  over  its  surface,  and  range  after  range  in  parallel 
lines  to  its  heights,  until  finally  the  continental  area  reached 
its  limit,  and  the  great  interior  basin  had  its  mountain-bor- 
ders completed :  on  the  east,  the  low  Appalachians,  and  the 
trap  ridges  of  the  Mesozoic ;  on  the  west,  the  massive  and  lofty 
Eocky  Mountain  chain,  with  the  parallel  ranges  over  its 
western  slopes. 

It  has  been  explained  on  page  243  that,  when  the  continent 
was  thus  far  completed,  there  occurred  a  change  in  the  region 
moved  by  the  forces.  The  high-latitude  oscillations  of  the 
Quaternary  then  began.  But  the  Pacific  and  Atlantic  forces 
may  have  occasioned  these  new  movements.  For  if,  in  the 
course  of  the  changes  through  the  geological  ages,  the  por- 


334  DYNAMICAL  GEOLOGY. 

tions  of  the  continental  crust  in  lower  latitudes,  thickened  by 
the  successive  formations,  and  stiffened  by  mountain-chains 
and  metamorphism,  had  become  less  yielding  than  those  of 
higher  latitudes,  the  pressure  from  contraction  would  have 
produced  its  oscillations  in  the  latter  rather  than  in  the 
former. 

Thus,  the  evolution  of  the  features  of  the  surface,  even  to 
the  terraces  made  along  the  river- valleys  in  the  last  of  the 
ages,  may  have  taken  place  through  one  system  of  forces 
originating  in  one  single  cause,  —  the  earth's  contraction  from 
cooling.  North  America,  which  is  here  appealed  to  for  ex- 
planations, affords  the  truest  and  clearest  illustration  of  the 
principles  involved,  because  it  lies  alone  between  the  two 
oceans,  the  Atlantic  and  Pacific,  with  the  nearest  continent, 
South  America,  to  the  west  of  its  meridians.  The  evolution, 
under  the  forces  from  the  two  directions,  went  forward  on  this 
account  with  great  regularity,  each  age  repeating  the  preceding 
in  the  direction  of  all  oscillations,  or  uplifts.  It  was  a  single 
isolated  individual  making  systematic  progress  throughout 
until  its  final  completion,  and  exhibits  truly  the  system  in  the 
earth's  development.  Europe,  in  contrast,  has  Africa  on  the 
south  and  Asia  on  the  east ;  it  is,  therefore,  full  of  complexities 
in  its  feature  lines  and  in  the  succession  of  events  that  make 
up  its  geological  history. 

4.  Formation  of  Mountain  Chains. 

1.  A  Geosynclinal,  or  downward  bend  of  the  Crust,  the  first 
step  in  ordinary  Mountain-making.  —  In  the  making  of  the 
Appalachians  there  was  first,  under  the  lateral  pressure,  a 
slowly  progressing  subsidence;  it  began  in,  or  before,  the 
Primordial  period,  the  commencing  era  of  the  Silurian,  and 
continued  in  progress  until  the  Carboniferous  age  closed.  As 
the  trough  deepened,  deposits  of  sediment,  and  sometimes  of 
limestone,  were  made,  that  kept  the  surface  of  the  region  near 
the  water  level ;  and,  when  the  trough  reached  its  maximum, 
there  were  40,000  feet  in  thickness  of  stratified  rock  in  it 


RESULTS   OF   THE   EARTH'S   CONTRACTION.         335 

(page  151),  and  this,  therefore,  was  the  depth  of  the  trough. 
The  Green  Mountains  began  in  a  similar  subsidence,  and  at 
the  same  time;  and  the  trough  was  kept  full  with  deposits  as 
it  progressed;  but  it  reached  its  maximum,  or  the  era  of 
catastrophe,  at  the  close  of  the  Lower  Silurian.  Such  facts 
are  in  the  history  of  many,  if  not  all,  mountains. 

2.  The  bottom  of  the  Geosynclinal  weakened  by  the  Heat  rising 
into  it  from  below.  —  As  planes  of  equal  temperature  within 
the  earth  have  a  nearly  uniform  distance  from  the  surface,  the 
accumulation  of  sedimentary  beds  in  sinking  trough  would 
occasion,  as  Herschel  long  since  urged,  the  corresponding  rising 
of  heat  from  below,  so  that,  with  40,000  feet  of  such  accumu- 
lations, a  given  isothermal  plane  would   have  been  raised 
40,000  feet.     Under  such  an  accession  of  heat,  the  bottom 
of  the  trough  would  have  been  greatly  weakened,  if  not  partly 
melted  off.     If  the  lower  surface  of  the  crust  had  dipped 
down  this  much  into  the  plastic  layer  that  was  beneath  it,  it 
would  have  been  actually  melted  off. 

3.  The  Heat  in  the  lower  part  of  the  trough  increased  by  the 
transformation  of  motion  into  heat  —  The  heat  from  the  trans- 
formation of  the  motion  of  the  crust  would  have  been  of  feeble 
amount,  if  the  motion  was  extremely  slow  and  regular.    But, 
with  fractures,  shovings,  and  crushing  accompanying  it,  the 
heat  from  the  rise  of  the  isogeothermal  would  have  been  much 
reinforced. 

4.  The  weakened  trough  yields  before  the  pressure.  —  The 
lateral  pressure,  acting  against  a  trough  thus  weakened,  would 
end,  as  Hunt  has  observed,  in  causing  a  collapse,  that  is,  a 
catastrophic  break  of  the  trough  below,  and  a  pressing  to- 
gether of  the  stratified  beds  within  it.     And  with  this  break 
the  shaping  of  the  mountain  would  begin. 

5.  Character  of  the  Mountain  thus  made.  —  Under  such  cir- 
cumstances the  stratified  rocks  would  be  folded,  profoundly 
broken,  shoved  along  fractures,  and  pressed  into  a  narrower 
space  than  they  occupied  before  ;  and  thus  they  would  become 
raised,  as  argued  by  Le  Conte,  above  their  former  level,  so  that 


336  DYNAMICAL  GEOLOGY. 

a  mountain  range  would  be  the  result,  even  without  any  actual 
uplift  of  the  crust  beneath.  The  crust  beneath  was  that  of 
the  geosyiiclinal ;  and  lateral  pressure,  however  powerful, 
could  not  possibly  have  raised  at  the  time  the  downward 
flexed  crust. 

6.  The  finished  Mountain  Range  a  Synclinorium.  —  Such  a 
mountain  range,  begun  in  a  geosynclinal  and   ending  in  a 
catastrophe  of  displacement  and  upturning,  is,  as  named  by 
the  author,  a  synclinorium,  it  owing  its  origin  to  the  progress 
of  a  geosynclinal.     (The  word  is  from  the  Greek  for  synclinal, 
and  o/oo?,  mountain)     Although  at  first  consisting  of  a  series 
of  parallel  folds  of  strata,  with  the  anticlinals  greatly  broken, 
—  the  anticlinals,  perhaps  two,  or  three,  or  more  miles  in 
height,  —  denudation,   after  pursuing  its  work   for  a  while, 
would  reduce  it  to  a  group  of  synclinal  ridges.     The  fractured 
anticlinals  are  easily  worn  away ;  while  the  synclinals  have 
the  elements  of  greater  permanence,  in  being  much  less  broken 
above,  and  in  having  their  rocks  folded  and  pressed  together, 
if  a  close  synclinal,  and  thus  made  firmer  and  more  durable, 
even  if  not  also  crystallized  by  metamorphism.     The  syncli- 
nals of  greatest  breadth  and  depth,  other  things  being  equal, 
should  become  ultimately  the  highest  of  the  mountain  ridges, 
because  more  material  is  embraced  in  them.     In  the  Taconic 
Mountains,  on  the  western  border  of  Massachusetts,  Mount 
Washington  (including  Mount  Everett)  and  Graylock  are  the 
high  peaks,  for  the  reason  just  explained.     Other  portions  of 
the  Taconic  range  are  made  of  narrower  portions  of  the  syn- 
clinal, and  are  less  elevated. 

7.  A  Mountain  Chain  may  comprise  Synclinoria  of  different 
ages.  —  The  Appalachian  chain  consists  of  (1)  mountains  of 
Archaean  rocks,  that  were  made  in  pre-Silurian  time ;  (2)  the 
Green  Mountains,  that  date  from  the  close  of  the   Lower 
Silurian;  and  (3)  the  Alleghanies,  that  were  formed  at  the 
close  of  the  Carboniferous  age.     The  Green  Mountains  began 
in  the  same  great  geosynclinal  with  the  Alleghanies ;  but  that 
northern  part  of  it  reached  its  completion  and  catastrophe 


RESULTS  OF  THE  EARTH'S  CONTRACTION.        337 

long  before  the  Alleghany  part,  probably  because  so  near  the 
Adirondack  border  of  the  stable  part  of  the  continent.  It  is 
probable  that  the  Archaean  portion  of  the  Appalachian  chain, 
which  includes  the  Blue  Ridge,  the  New  Jersey  Highlands, 
continued  in  Dutchess  County,  N.  Y.,  and  the  Adirondacks, 
corresponds  to  another  older  synclinorium.  Thus  a  mountain 
chain  may  comprise  several  synclinoria  made  at  widely  differ- 
ent epochs. 

The  several  areas  of  the  Triassico-Jurassic  sandstone  (page 
159)  were  areas  of  subsidence  or  sinking  troughs,  and  of  sedi- 
mentary accumulations  in  progress  in  each  trough ;  and  the 
geosynclinal,  in  each  case,  ended  in  catastrophe,  as  exhibited 
in  upturned  or  displaced  rocks,  and  in  many  lines  of  great 
fractures,  giving  exit  to  igneous  rocks.  The  progress  was  like 
that  in  the  case  of  a  synclinorium,  although  no  true  mountain- 
chain  was  made. 

8.  Metamorphism  and  other  attendant  effects.  —  The  heat 
developed  through  the  transformation  of  motion,  added  to 
that  rising  into  the  strata  from  below,  would  produce  all  the 
consolidation  and  crystallization  which  has  been,  in  any  case, 
observed ;  and  would  cause,  as  lighter  effects,  the  change  of 
brown  oxyd  of  iron  to  red  oxyd,  thereby  reddening  sandstones 
and  clays,  or  make  other  decompositions  in  which  red  oxyd 
of  iron  is  developed ;  and  also  debituminize  mineral  coal,  and 
evolve  mineral  oil  from  black  hydrocarbon  shales  (like  the 
Black  shale  of  the  Hamilton),  to  be  condensed  in  cavities  in 
overlying  strata. 

The  heat  engendered,  and  causing  the  metamorphism,  may 
be  so  great  as  to  reduce  the  rock  subjected  to  it  to  a  plastic 
condition,  and  make  granite,  or  some  other  granite-like  rock ; 
in  which  case  granite  might  be  made  to  fill  opened  fissures, 
like  a  true  igneous  rock,  or  to  constitute  the  core  of  a  long 
mountain  range,  like  that  of  the  Sierra  Nevada. 

9.  The  region  of  a  Synclinorium  becomes  added  to  the  stable 
part  of  the  Continent  —  The  region  that  had  been  long  under- 
going subsidence  becomes,  after  the  upturning  and  consolida- 

15  V 


DYNAMICAL   GEOLOGY. 

tion,  stiff,  unyielding,  and  stable ;  and  the  locus  of  the  next 
progressing  geosynclinal  on  the  same  continental  border  will 
be  situated  to  one  or  the  other  side  of  it.  After  the  Alle- 
ghany  range  was  made,  there  was,  in  the  next  or  Triassic  pe- 
riod, a  new  trough,  or  rather  a  series  of  them,  more  to  the 
eastward,  in  which  the  Triassico-Jurassic  beds  were  laid 
down. 

10.  Geanticlinals  as  well  as  Geosynclinals  concerned  in  Moun- 
tain-making. —  In  the  movements  of  the  earth's  crust  there 
would  necessarily  be  upward  as  well  as  downward  flexures, 
—  that  is,  geanticlinals  as  well  as  geosynclinals.     The  Appa- 
lachians, as  explained  above,  may,  when  first  made,  have  stood 
up  in  lofty  ridges,  without  having  undergone  any  uplifting 
from  an  elevation  of  the  crust  underneath.     But,  however  this 
be,  the  region  actually  experienced  elevation  before  the  Triassic 
period  opened,  as  is  proved  by  the  position  of  the  Triassic 
beds ;  and  this  took  place  through  a  gentle  upward  bending 
of  the  crust,  such  a  bending  becoming  possible  after  (although 
not  before)  the  region  of  the  Appalachians  had  become  a 
portion  of  the  stable  part  of  the  continent. 

The  Rocky  Mountains  in  the  Cretaceous  era  were  10,000 
feet  below  their  present  level,  the  sea  covering  them.  They 
were  raised  as  a  whole,  during  the  Tertiary,  through  a  low 
geanticlinal.  The  last  geosynclinals  were  more  local  than  the 
preceding,  because  the  crust  had  become  stiffened  by  its  pli- 
cated and  solidified,  and  partly  crystallized,  coatings,  as  well 
as  by  thickening  beneath ;  and,  therefore,  while  the  Tertiary 
movements  were  in  progress,  the  part  of  the  force  not  ex- 
pended in  producing  them  carried  forward  an  upward  bend,  or 
geanticlinal,  of  the  vast  Rocky  Mountain  region  as  a  whole. 

11.  Anticlinoria  of  the  Atlantic  Border  of  North  America,  - 
An  upward  bend  of  the  crust,  or  geanticlinal,  is  of  itself  an 
elevation;  and  such  an  elevation  is*  an  anticlinorium.     The 
Cincinnati  uplift,  described  on  page  91,  is  an  anticlinorium, 
made,  parallel  with  the  Appalachians,  after  the  Lower  Silu- 
rian era,  contemporaneously  with  the  making  of  the  Green 
Mountains. 


RESULTS   OF   THE   EARTH'S   CONTRACTION.        339 

While  the  geosynclinal  preparatory  for  the  making  of  the 
Appalachians  and  those  for  the  Triassico-Jurassic  formations 
were  going  forward,  through  Paleozoic  and  Mesozoic  time, 
there  was,  along  the  Atlantic  Border,  near  or  outside  of  the 
present  coast-line  a  geanticlinal  in  progress,  or  sea-border  an- 
ticlinorium.  It  was  the  first  effect  of  the  pressure  from  the 
ocean- ward ;  and  the  geosynclinal  was  the  second. 

Proofs  of  this  are  found  (1)  in  the  necessity  that  one  move- 
ment should  have  taken  place  as  a  counterpart  to  the  other, 
since  the  depression  of  a  geosynclinal  thousands  of  feet  would 
push  out  from  beneath  it  an  equivalent  mass  of  plastic  rock ; 
and  this  would  involve  a  bulging  on  one  side  or  the  other ; 
(2)  in  the  fact  that  obliquely  upward  pressure  from  the  ocean- 
ward,  however  slight  the  obliquity,  would  first  have  made  an 
upward  bend,  and  beyond  this  the  downward  bend ;  and  (3) 
in  the  character  of  the  remains  of  marine  life,  or  else  its  ab- 
sence, in  the  sea-border  rocks,  through  a  large  part  of  Paleo- 
zoic and  Mesozoic  time,  showing  that  a  barrier  of  some  kind 
existed  along  the  sea-border. 

The  facts  from  the  fossils  are  these :  While,  in  the  early 
part  of  the  Lower  Silurian,  the  species  of  the  Eastern  border 
are  like  those  of  Europe  in  some  points,  this  is  not  so  in  the 
long  Trenton  period,  so  that  the  barrier  must  then  have  ex- 
isted. In  the  Carboniferous  rocks  of  Eastern  Pennsylvania 
there  are  almost  no  marine  fossils;  and  again,  in  those  of 
the  following  Triassic  and  Jurassic  eras,  none  at  all.  It  was 
not  until  the  Cretaceous  period  that  the  coast  was  open  to 
the  ocean,  through  a  disappearance  of  the  geanticlinal  barrier. 
The  Cretaceous  rocks  abound  in  marine  fossils. 

Anticlinoria  appear  generally  to  have  faded  out,  as  gravity 
was  against  their  permanence ;  and  that  in  the  region  of  Cin- 
cinnati, extending  southwestward  to  Tennessee,  is  one  of  the 
few  permanent  ones. 

12.  Geanticlinal  effects  over  the  Continents  greatest  and  most 
permanent,  and  Geosynclinal  least  so,  in  the  Tertiary  and  Quater- 
nary Ages.  —  After  the  crust  had  become  thickened,  by  the 


340  DYNAMICAL   GEOLOGY. 

earth's  internal  cooling,  through  the  ages,  and  had  been  stiff- 
ened also  by  the  plication  and  solidification,  and  partly  the 
crystallization,  of  the  strata  of  the  supercrust,  geosynclinals 
became  less  a  possibility,  and  therefore  of  diminished  extent ; 
and  consequently  the  chief  movement  caused  by  the  ever- 
continuing  lateral  pressure  was  an  upward  one.  Hence  it  is 
that  the  mountain-chains  received  their  great  height  so  largely 
in  the  Tertiary ;  and  hence  also  the  vastness  of  the  areas  over 
the  earth's  surface  that  were  affected  by  single  movements, 
such  as  the  high-latitude  movements  of  the  Quaternary. 
There  was,  also,  a  downward  bending  over  those  higher  lati- 
tudes, in  the  Quaternary,  and  another  in  the  warm  parts  of 
the  oceans,  —  the  coral-island  subsidence.  But  these  bear  the 
character  of  the  times  in  the  extent  of  surface  involved,  and 
are  wholly  unlike  the  mountain-making  geosynclinals  of  ear- 
lier time.  It  is  probable  that  the  Pacific  coral-island  subsi- 
dence, or  geosynclinal,  was  the  counterpart  of  the  geanticlinals 
over  the  continents  of  the  later  Tertiary  and  early  Quater- 
nary. 

13.  Fractures  and  outflows  of  igneous  rocks  become  numerous, 
after  the  crust  has  become  too  much  stiffened  to  bend  easily.  — 
Great  floods  of  doleryte  and  trachyte  were  poured  out  over  the 
Eocky  Mountain  slope,  after  the  close  of  the  Cretaceous  pe- 
riod. The  previous  plications  and  solidifications  of  the  strata 
involved  in  the  making  of  the  various  ranges  of  mountains  — - 
the  Sierra  Nevada  and  the  Coast  ranges  on  the  west,  and  the 
Wahsatch  and  Cretaceous  mountains  on  the  east  —  had  left 
the  crust  firm  and  unyielding ;  and,  being  too  stiff  to  bend,  it 
broke,  and  out  leaped  the  fiery  floods.  It  had  broken  at 
times  before;  but  at  this  time  the  fractures  became  much 
more  numerous,  and  the  floods  of  rock  more  extensive. 
Moreover,  from  this  era  appears  to  date  the  opening  of  the 
great  volcanoes  of  the  Shasta  range.  In  fact,  the  larger  part 
of  the  volcanic  eruptions  of  the  world  are  probably  of  Tertiary 
and  later  origin. 

Fractures  giving  outlet  to  igneous  eruptions  have  probably 


RESULTS   OF  THE  EARTH'S  CONTRACTION.        341 

been,  in  all  cases,  consequences  either  (1)  of  catastrophe  in  a 
geosynclinal,  as  in  the  Triassico- Jurassic  areas  of  the  Atlantic 
border,  or  (2)  catastrophe  in  a  geanticlinal,  when  the  crust 
was  too  stiff  for  geosynclinal  bendings,  as  over  the  Pacific 
slope  of  the  Rocky  Mountains ;  and  the  latter  became  far  the 
most  common  in  the  later  part  of  geological  time. 

The  principles  in  the  earth's  evolution  above  presented 
have  been  elucidated  by  reference  mainly  to  facts  from  North 
America.  If  true  for  that  continent,  the  same  must  be  law 
for  all  continents.* 

14.  Mountain-making  slow  work.  —  To  obtain  an  adequate 
idea  of  the  way  in  which  lateral  pressure  has  worked,  it  is 
necessary  to  remember  that  mountain  elevation  has  taken 
place  after  immensely  long  periods  of  quiet  and  gentle  oscil- 
lations. After  the  beginning  of  the  Primordial,  the  first  period 
of  disturbance  in  North  America,  of  special  note,  was  that  at 
the  close  of  the  Lower  Silurian,  in  which  the  Green  Mountains 
were  finished ;  and  if  time,  from  the  beginning  of  the  Silurian 
to  the  present,  included  only  48  millions  of  years  (page 
245),  the  interval  between  the  beginning  of  the  Primordial 
and  the  uplifts  and  metamorphism  of  the  Green  Mountains 
was  at  least  20  millions  of  years.  The  next  epoch  of  moun- 
tain-making on  the  Atlantic  border  was  after  the  Devonian 
in  Nova  Scotia  and  New  Brunswick ;  on  the  above  basis,  it 
occurred  30  millions  of  years  from  the  beginning  of  the 
Primordial.  The  next  epoch  of  disturbance  was  that  at  the 
close  of  the  Carboniferous  era,  in  which  the  Alleghanies 
were  folded  up ;  by  the  above  estimate  of  the  length  of 
time,  36  millions  of  years  after  the  commencement  of  the 
Silurian;  so  that  the  Alleghanies  were  at  least  36,000,000 
of  years  in  making,  the  preparatory  subsidence  having  be- 
gun as  early  as  the  beginning  of  the  Silurian.  The  next  on 
the  Atlantic  border  was  that  of  the  displacements  of  the 

*  For  a  fuller  discussion  of  the  subject  here  briefly  presented,  see  a  memoir 
in  the  American  Journal  of  Science  for  June,  July,  August,  and  September, 
1873,  Vols.  V.  and  VI. 


342  CONCLUSION. 

Triassico-Jurassic  sandstone,  and  the  accompanying  igneous 
ejections,  which  occurred  before  the  Cretaceous  era,  —  at  least 
5  millions  of  years,  on  the  above  estimate  of  the  length  of 
time,  after  the  Appalachian  revolution.  Thus  the  lateral 
pressure  resulting  from  the  earth's  contraction  required  an 
exceedingly  long  time,  in  order  to  accumulate  force  sufficient 
to  produce  a  general  yielding  and  plication  or  displacement 
of  the  beds,  and  start  off  a  new  range  of  prominent  elevations 
over  the  earth's  crust. 

CONCLUDING  REMARKS. 

Geology  may  seem  to  be  audacious  in  its  attempts  to  unveil 
the  mysteries  of  creation.  Yet  what  it  reveals  are  only  some 
of  the  methods  by  which  the  Creator  has  performed  his  will ; 
and  many  deeper  mysteries  it  leaves  untouched. 

It  brings  to  view  a  perfect  and  harmonious  system  of  life, 
but  affords  no  explanation  of  the  origin  of  life,  or  of  any  of 
nature's  forces. 

It  accounts  for  the  forms  of  continents ;  but  it  tells  nothing* 
as  to  the  source  of  that  arrangement  of  the  wide  and  narrow 
continents  and  wide  and  narrow  oceans  that  was  necessary 
to  the  grand  result. 

It  teaches  that  strata  were  made  in  many  successions  as 
the  continents  lay  balancing  near  the  water's  level,  sometimes 
just  above  the  surface,  sometimes  a  little  below ;  but  it  does 
not  explain  how  it  happened  that  the  amount  of  water  was 
of  exactly  the  right  quantity  to  fill  the  great  basin,  and  admit 
of  oscillations  of  the  land  beneath  or  above  its  surface  by  only 
small  changes  of  level ;  for  if  the  water  had  been  a  few  hun- 
dred feet  below  the  level  it  now  has,  the  continents  would 
have  remained  mostly  without  their  marine  strata,  and  the 
plan  of  progress  would  have  proved  a  failure ;  or  if  as  much 
above  its  present  level,  the  land  through  the  earlier  ages  would 
have  been  sunk  to  depths  comparatively  lifeless,  with  no  less 
fatal  results  both  to  the  series  of  rocks  and  the  system  of 


CONCLUSION.  343 

marine  and  terrestrial  life ;  and  in  the  end  there  would  have 
been  broad  and  narrow  strips  of  dry  land  and  archipelagoes, 
in  place  of  the  expanded  Orient  and  Occident. 

It  may  be  said  to  have  searched  out  the  mode  of  develop- 
ment of  a  world.  Yet  it  can  point  to  no  physical  cause  of 
that  prophecy  of  Man  which  runs  through  the  whole  history ; 
which  was  uttered  by  the  winds  and  waves  at  their  work  over 
the  sands,  by  the  rocks  in  each  movement  of  the  earth's  crust, 
and  by  every  living  thing  in  the  long  succession,  until  Man 
appeared  to  make  the  mysterious  announcements  intelligible. 
For  the  body  of  Man  was  not  made  more  completely  for  the 
service  of  the  soul,  than  the  earth,  in  all  its  arrangements 
from  beginning  to  end,  for  the  spiritual  being  that  wras  to 
occupy  it.  In  Man,  the  bones  are  not  merely  the  jointed 
framework  of  an  animal,  but  a  framework  shaped  throughout 
with  reference  to  that  erect  structure  which  befits  and  can 
best  serve  Man's  spiritual  nature.  The  feet  are  not  the 
clasping  and  climbing  feet  of  a  monkey ;  they  are  so  made  as 
to  give  firmness  to  the  tread  and  dignity  to  the  bearing  of  the 
being  made  in  God's  image.  The  hands  have  that  fashioning 
of  the  palm,  fingers,  and  thumb,  and  that  delicacy  of  the 
sense  of  touch,  which  adapt  them  not  only  to  feed  the  mouth, 
but  to  contribute  to  the  wants  of  the  soul  and  obey  its 
promptings.  The  arms  are  not  for  strength  alone,  —  for  they 
are  weaker  than  in  many  a  brute,  —  but  to  give  the  greater 
power  and  expression  to  the  thoughts  that  issue  from  within. 
The  face,  with  its  expressive  features,  is  formed  so  as  to  re- 
spond not  solely  to  the  emotions  of  pleasure  and  pain,  but  to 
shades  of  sentiment  and  interacting  sympathies  the  most 
varied,  high  as  heaven  and  low  as  earth,  —  ay,  lower,  in  de- 
based human  nature.  And  the  whole  being,  body,  limbs,  and 
head,  with  eyes  lo'oking,  not  toward  the  earth,  but  beyond  an 
infinite  horizon,  is  a  majestic  expression  of  the  divine  feature 
in  Man,  and  of  the  infinitude  of  his  aspirations. 

So  with  the  earth,  Man's  world-body.  Its  rocks  were  so 
arranged,  in  their  formation,  that  they  should  best  serve  Man's 


344  CONCLUSION. 

purposes.  The  strata  were  subjected  to  metamorphism,  and 
so  crystallized  that  he  might  be  provided  with  the  most  per- 
fect material  for  his  art,  —  his  statues,  temples,  and  dwellings ; 
at  the  same  time  they  were  filled  with  veins,  in  order  to  supply 
him  with  gold  and  silver  and  other  treasures.  The  rocks  were 
also  made  to  enclose  abundant  beds  of  coal  and  iron  ore,  that 
Man  might  have  fuel  for  his  hearths  and  iron  for  his  utensils 
and  machinery.  Mountains  were  raised  to  temper  hot  climates, 
to  diversify  the  earth's  productiveness,  and,  pre-eminently,  to 
gather  the  clouds  into  river-channels,  thence  to  moisten  the 
fields  for  agriculture,  afford  facilities  for  travel,  and  supply 
the  world  with  springs  and  fountains. 

The  continents  were  clustered  mostly  in  one  hemisphere 
to  bring  the  nations  into  closer  union ;  and  the  two  having 
climates  and  resources  the  best  for  human  progress,  —  the 
northern  Orient  and  Occident,  —  were  separated  by  a  narrow 
ocean,  that  the  great  mountains  might  be  on  the  remoter  bor- 
ders of  each,  and  all  the  declivities,  plains,  and  rivers  be  turned 
toward  one  common  channel  of  intercourse.  So,  also,  the 
species  of  life,  both  of  plants  and  animals,  were  appointed 
to  administer  to  Man's  necessities,  moral  as  well  as  physical. 

Besides  these  beneficent  provisions,  the  forces  and  laws  of 
nature  were  particularly  adapted  to  Man,  and  Man  to  those 
laws,  so  that  he  should  be  able  to  take  the  oceans,  rivers,  and 
winds  into  his  service,  and  even  the  more  subtle  agencies, 
heat,  light,  and  electricity ;  and  the  adjustments  were  made 
with  such  precision  that  the  face  of  the  earth  is  actually 
fitted  hardly  less  than  his  own  to  respond  to  his  inner  being : 
the  mountains  to  his  sense  of  the  sublime,  the  landscape,  with 
its  slopes,  its  trees,  its  flowers,  to  his  love  of  the  beautiful,  and 
the  thousands  of  living  species,  in  their  diversity,  to  his  various 
emotions  and  sentiments.  The  whole  wo*rld,  indeed,  seems 
to  have  been  made  almost  a  material  manifestation,  in  multi- 
tudinous forms,  of  the  elements  of  his  own  spiritual  nature, 
that  it  might  thereby  give  wings  to  the  soul  in  its  heavenward 
aspirings.  It  may  therefore  be  said  with  truth  that  Man's 


CONCLUSION.  345 

spirit  was  considered  in  the  ordering  of  the  earth's  structure 
as  well  as  in  that  of  his  own  body. 

It  is  hence  obvious  that  the  earth's  history,  which  it  is  the 
object  of  Geology  to  teach,  is  the  true  introduction  to  human 
history. 

It  is  also  certain  that  science,  whatever  it  may  accomplish 
in  the  discovery  of  causes  or  methods  of  progress,  can  take  no 
steps  toward  setting  aside  a  Creator.  Far  from  such  a  result, 
it  clearly  proves  that  there  has  been  not  only  an  omnipotent 
hand  to  create,  and  to  sustain  physical  forces  in  action,  but 
an  all- wise  and  beneficent  Spirit  to  shape  all  events  toward  a 
spiritual  end. 

Man  may  well  feel  exalted  to  find  that  he  was  the  final 
purpose  when  the  word  went  forth  in  the  beginning,  LET 
LIGHT  BE.  And  he  may  thence  derive  direct  personal  assur- 
ance that  all  this  magnificent  preparation  is  yet  to  have  a 
higher  fulfilment  in  a  future  of  spiritual  life.  This  assurance 
from  nature  may  seem  feeble.  Yet  it  is  at  least  sufficient  to 
strengthen  faith  in  that  Book  of  books  in  which  the  promise 
of  that  life  and  "  the  way  "  are  plainly  set  forth. 


15* 


APPENDIX. 


A.  —  Catalogue  of  American  Localities  of  Fossils. 

THE  following  catalogue  of  American  localities  of  fossils  contains 
only  some  of  the  more  important,  and  is  intended  for  the  conven- 
ience especially  of  the  student-collector. 

Localities  of  Fossils. 

Acadian  Group.  —  Coldbrook,  Ratcliffe's  Millstream,  St.  John,  New 
Brunswick.  —  Long  Arm  of  Canada  Bay,  Newfoundland. 

Potsdam  Group.  —  Swanton,  Vt.  —  Braintree,  Mass.  —  Keeseville  (at 
"High  Bridge"),  Alexandria,  Troy,  N.  Y.  —  Chiques  Ridge,  Pa.  —Falls  of 
St.  Croix,  Osceola  Mills,  Trempaleau,  Wisconsin.  —  Lansing,  Iowa.  —  S*t. 
Ann's,  Isle  Perrot,  C.  W.  — Near  Beauharnois  on  Lake  St.  Louis,  C.  E. 

Calciferous.  —  Mingan  Islands,  St.  Timothy,  and  near  Beauharnois, 
C.  E.  —  Grand  Trunk  Railway  between  Brockville  and  Prescott,  St.  Ann's, 
Isle  Perrot,  C.  W.  —  Amsterdam,  Fort  Plain,  Canajoharie,  Chazy,  Lafarge- 
ville,  Ogdenshurg,  N.  Y. 

Quebec  Group.  —  Mingan  Islands,  Point  Levi,  Philipsburg,  and  near 
Beauharnois,  C.  E.  —  Point  Rich,  Cow  Head,  Newfoundland.  —  Cuts  in  Black 
Oak  Ridge  and  Copper  Ridge,  Knoxville  and  Ohio  Railroad,  Tenn.  —  Malade 
City,  Idaho. 

Chazy  Limestone.  —  Chazy,  Gal  way,  Westport,  N.  Y.  —  One  to  three 
miles  north  of  "the  Mountain"  Island  of  Montreal,  C.  E. — St.  Joseph's 
Island,  Sault  Ste.  Marie,  C.  W.  —  Knoxville,  Lenoir's,  Bull's  Gap,  Kings- 
port,  Tenn. 

Bird's-eye  Limestone.  — Amsterdam,  Little  Falls,  Fort  Plain,  Adams, 
Watertown,  N.  Y. 

Black  River  Limestone.  —  Watertown,  N.  Y.  —  Ottawa,  C.  W.  — 
Island  of  Montreal,  and  near  Quebec,  C.  E. 

Trenton  Limestone.  —  Adams,  Watertown,  Boonville,  Turin,  Jackson- 
burg,  Little  Falls,  Lowville,  Middleville,  Fort  Plain,  Trenton  Falls,  N.  Y.  — 
Pine  Grove,  Aaronsburg,  Potter's  Fort,  Milligan's  Cove,  Pa.  —  Highgate 


APPENDIX.  347 

Springs,  Vt.  —  Montmorency  Falls  and  Beauport  Quarries  near  Quebec, 
Island  of  Montreal  (quarries  north  of  the  city),  C.  E.  —  Ottawa,  Belleville, 
Trenton  (G.  T.  R.  R.,  west  of  Kingston),  C.  W.  —  Copper  Bay,  Mich.  —  El- 
kader  Mills,  Turkey  River,  Dubuque,  Iowa.  —  Falls  of  St.  Anthony,  St. 
Paul,  Mineral  Point,  Cassville,  Beloit,  Quimby's  Mills  near  Benton,  Wis.  — 
Warren,  Rockton,  "Winslow,  Dixon,  Freeport,  Cedarville,  Savanna,  Rockford, 
111.  —  Murfreesborough,  Columbia,  Lebanon,  Tenn. 

Utica  Slate.  —  Turin,  Martinsburg,  Lorraine,  Worth,  Utica,  Cold  Spring, 
Oxtungo  and  Osquago  Creeks  near  Fort  Plain,  Mohawk,  Rouse's  Point,  N.  Y. 

—  Rideau  River  along  railroad  at  Ottawa,  bed  of  river  two  miles  above,  C.  W. 
Cincinnati   Group.  —  Pulaski,    Rome,    Lorraine,    Boonville,    N.    Y.  — 

Penn's  Valley,  Milligan's  Cove,  Pa.  —  Oxford,  Cincinnati,  Lebanon,  0.  — 
Madison,  Richmond,  Ind.  —  Anticosti,  opposite  Three  Rivers,  C.  E.  — 
Weston  on  the  Humber  River,  nine  miles  west  of  Toronto,  C.  W.  —  Little 
Makoqueta  River,  Iowa.  —  Savannah,  Green  Bay,  Wis.  —  Thebes,  Alexander 
County  ;  Savanna,  Carroll  County  ;  Scales's  Mound,  Jo  Daviess  County  ; 
Oswego,  Yorkville,  Kendall  County  ;  Naperville,  Dupage  County  ;  Wilming- 
ton, Will  County,  111.  —  Cape  Girardeau,  Mo.  —  Drummond's  Island,  Mich. 

—  Nashville,  Columbia,  Knoxville,  Tenn. 

Medina  Sandstone.  —  Lockport,  Lewiston,  Medina,  Rochester,  N.  Y.  — 
Long  Narrows  below  Lewistown,  Pa.  —  Dun  das,  C.  W. 

Clinton  Group.  —  Lewiston,  Lockport,  Reynolds  Basin,  Brockport,  Roch- 
ester, Wolcott,  New  Hartford,  N.  Y.  —  Thorold  on  Welland  Canal,  Hamilton, 
Ancaster,  Dundas,  C.  W.  —  Hanover,  Ind. 

Niagara.  —  Lewiston,  Lockport,  Gosport,  Rochester,  Wolcott,  N.  Y.  — 
Thorold,  Hamilton,  Ancaster,  C.  W.  —  Anticosti,  C.  E.  —  Arisaig,  Nova 
Scotia.  —  Racine,  Waukesha,  Wis.  —  Sterling,  Grafton,  Savanna,  Chicago, 
Joliet,  111.  —  Marblehead  on  Drummond's  Island,  Michigan.  —  Springfield, 
Cedarville,  Ohio.  —  Delphi,  Waldron,  Jeffersonville,  Madison,  Logansport, 
Peru,  Ind.  —  Louisville,  Ky.  —  The  "glades  "  of  West  Tennessee.  (Coral- 
line Limestone.  —  Schoharie,  N.  Y.) 

Onondaga  Salt  Group.  —  Buffalo,  Williamsville,  Waterville,  Jerusalem 
Hill  (Herkimer  County),  N.  Y.  —  Gait,  Guelph  (G.  T.  R.  R.),  C.  W. 

Lower  Helderberg  Limestones.  —  Dry  Hill,  Jerusalem  Hill  (Herki- 
mer County),  Sharon,  East  Cobleskill,  Judd's  Falls,  Cherry  Valley,  Carlisle, 
Schoharie,  Clarksville,  Athens,  N.  Y.  —  Pembroke,  Parlin  Pond,  Me.  — 
Gaspe,  C.  E.  —  Arisaig,  East  River,  Nova  Scotia.  —  Peach  Point,  opposite 
Gibraltar,  Ohio.  —  Thebes,  Devil's  Backbone,  111.  —  Bailey's  Landing,  Mo.  — 
"  Glades  "  of  Wayne  and  Hardin  Counties,  Tenn. 

Oriskany  Sandstone.  —  Oriskany,  Vienna,  Carlisle,  Schoharie,  Pucker 
Street,  Catskill  Mountains,  N.  Y.  —  Cumberland,  Md.  —  Moorestown  and 
Frankstown,  Pa.  —  Bald  Bluffs,  Jackson  County,  111.  —  Four  miles  S.  W. 
of  St.  Mary's,  Ste.  Genevieve  County,  Mo. 

Cauda-galli  Grit.  —  Schoharie  (Fucoides  Cauda-galli),  N.  Y. 

Schoharie  Grit.  —  Schoharie,  Cherry  Valley,  N.  Y. 

Upper  Helderberg  Limestones.  —  Black  Rock,  Buffalo,  Williamsville, 


348  APPENDIX. 

Lancaster,  Clarence  Hollow,  Stafford,  Le  Roy,  Caledonia,  Mendon,  Auburn, 
Onondaga,  Cassville,  Babcock's  Hill,  Schoharie,  Cherry  Valley,  Clarksville, 
1ST.  Y.  —  Port  Colborne,  and  near  Cayuga,  C.  W.  —  Columbus,  Delaware, 
White  Sulphur  Springs,  Sandusky,  Ohio.  —  Mackinac,  Little  Traverse  Bay, 
Dundee,  Monguagon,  Mich.  —  North  Vernon,  Charlestown,  Kent,  Hanover, 
Jefferson ville,  Ind.  —  Louisville,  Ky. 

Marcellus  Shales.  —  Lake  Erie  shore,  ten  miles  S.  of  Buffalo,  Lancaster, 
Alden,  Avon,  Leroy,  Marcellus,  Manlius,  Cherry  Valley,  N.  Y. 

Hamilton  Group.  —  Lake  Erie  shore,  Eighteen  Mile  Creek,  Hamburg, 
Alden,  Darien,  York,  Moscow,  East  Bethany,  Bloomfield,  Bristol,  Seneca 
Lake,  Cayuga  Lake,  Skaneateles  Lake,  Moravia,  Pompey,  Cazenovia,  Delphi, 
Bridgewater,  Richland,  Cherry  Valley,  Seward,  Westford,  Milford,  Portland- 
ville,  N.  Y.  —  Widder  Station  (G.  T.  R.  R.),  near  Port  Sarnia,  C.  W.  —  New 
Buffalo,  Independence,  Rockford,  Iowa. — Devil's  Bake  Oven,  Jackson 
County,  Moline,  Rock  Island,  111.  —  Grand  Tower,  Mo.  —  Thunder  Bay, 
Little  Traverse  Bay,  Mich.  —  Jefferson  ville,  Ind.  —  Nictaux,  Bear  River, 
Moose  River,  Nova  Scotia. 

Geiiesee  Shale.  —  Banks  of  Seneca  and  Cayuga  Lakes,  Lodi  Falls,  Mount 
Morris,  two  miles  south  of  Big  Stream  Point,  Yates  County,  N.  Y.  — 
(Genesee  or  Portage.  —  Delaware,  Ohio.  —  Rockford,  North  Vernon,  Ind. 
—  Danville,  Ky.) 

Portage  Group.  —  Eighteen  Mile  Creek  on  Lake  Erie,  Chautauqua  Lake, 
Genesee  River  at  Portage,  Flint  Creek,  Cashaqua  Creek,  Nunda,  Seneca  and 
Cayuga  Lakes,  N.  Y. 

Chemung  Group. — Rockville,   Philipsburg,   Jasper,   Greene,   Chemung. 
Narrows,  Troopsville,  Elmira,    Ithaca,  Waverly,  Hector,  Enfield,  Franklin, 
N.  Y.  -  Gaspe,  C.  E. 

Catskill  Group.  —  Fossils  rare.  —  Richmond's  quarry  above  Mount  Up- 
ton on  the  Unadilla,  Oneonta,  Oxford,  Steuben  County,  south  of  the  Canis- 
teo,  N.  Y. 

Subcarboniferous.  —  Burlington,  Keokuk,  Columbus,  Iowa.  —  Quincy, 
Warsaw,  Alton,  Kaskaskia,  Chester,  111.  —  Crawfordsville,  Greencastle, 
Bloomington,  Spergen  Hill,  New  Providence,  Ind.  —  Hannibal,  St.  Genevieve, 
St.  Louis,  Mo.  —  Willow  Creek,  Battle  Creek,  Marshal,  Moscow,  Jonesville, 
Holland,  Grand  Rapids,  Mich.  —  Mauch  Chunk,  Pa.  —  Newtonville,  Ohio.  — 
Ice's  Ferry,  on  Cheat  River,  Monongalia  County,  W.  Va.  —  Red  Sulphur 
Springs,  Pittsburg  Landing,  White's  Creek  Springs,  Waynesville,  Cowan, 
Tenn.  —  Big  Bear  and  Little  Bear  Creeks,  Big  Crippled  Deer  Creek,  Miss.  — 
Clarksville,  Huntsville,  Ala.  —  Windsor,  Horton,  Nova  Scotia. 

Carboniferous.  —  South  Joggins,  Pictou,  Sydney,  Nova  Scotia.  — Wilkes- 
barre,  Shamokin,  Tamaqua,  Pottsville,  Minersville,  Tremont,  Greensburg, 
Carbondale,  Port  Carbon,  Lehigh,  Trevorton,  Johnstown,  Pittsburg,  Pa.  — 
Pomeroy,  Marietta,  Zanesville,  Cuyahoga  Falls,  Athens,  Yellow  Creek,  Ohio. 
—  Charlestown,  Clarksburg,  Kanawha,  Salines,  Wheeling,  W.  Va.  —  Saline 
Company's  Mines,  Gallatin  County  ;  Carlinville,  Hodges  Creek,  Macoupin 
County  ;.  Colchester,  McDonough  County;  Duquoin,  Perry  County;  Mur- 


APPENDIX.  349 

physborough,  Jackson  County  ;  Lasalle  ;  Morris,  Mazon,  and  Waupecan  Creeks, 
Grundy  County  ;  Danville,  Pettys'  Ford,  Vermilion  County  ;  Paris,  Edgar 
County  ;  Springfield,  111.  —  Perrysville,  Eugene,  Newport,  Horseshoe  of  Little 
Vermillion,  Verniilliori  County  ;  Durkee's  Ferry,  near  Terre  Haute,  Vigo 
County  ;  Lodi,  Parke  County  ;  Merom,  Sullivan  County,  Ind.  —  Bell's,  Casey's, 
and  Union  Mines,  Crittenden  County  ;  Hawesville  and  Lewisport,  Hancock 
County  ;  Breckenridge,  Giger's  Hill,  Mulford's  Mines,  and  Thompson's  Mine, 
Union  County  ;  Providence  and  Madisonville,  Hopkin's  County  ;  Bonhar- 
bour,  Daviess  County,  Ky.  —  Muscatine,  Alpine  Dam,  Iowa.  —  Leavenworth, 
Indian  Creek,  Grasshopper  Creek,  Juniata,  Manhattan,  Kansas.  —  Rockwood, 
Emory  Mines,  Coal  Creek,  Careyville,  Tenn.  —  Tuscaloosa,  Ala. 

Triassic.  —  Southbury,  Middlefield,  Portland,  Conn.  —  Turner's  Falls, 
Sunderland,  Mass. — Phcenixville,  Pa. — Richmond,  Va.  —  Deep  River  and 
Dan  River  Coal-fields,  N.  C. 

Cretaceous.  —  Upper  Freehold,  Middletown,  Marlborough,  Blue  Ball, 
Monmouth  County  ;  Pemberton,  Vincenton,  Burlington  County  ;  Black- 
woodtown,  Camden  County  ;  Mullica  Hill,  Gloucester  County  ;  Woods- 
town,  Mannington,  Salem  County  ;  New  Egypt,  Ocean  County,  N.  J. 
—  Warren's  Mill,  Itawamba  County  ;  Tishomingo  Creek,  R.  R,  cuts,  Hare's 
Mill,  Carrollsville,  Tishomingo  County  ;  Plymouth  Bluff,  Lowndes  County  ; 
Cha walla  Station  (M.  &  C.  R.  R.),  Ripley,  Tippah  County  ;  Noxubee,  Macon, 
Noxubee  County  ;  Kemper,  Pontotoc  and  Chickasaw  Counties,  Miss.  — 
Finch's  Ferry,  Prairie  Bluff,  on  Alabama  River  ;  Choc  taw  Bluff,  on  Black 
Warrior  River  ;  Greene,  Marengo,  and  Lowndes  Counties,  Ala.  —  Fox  Hills, 
Sage  Creek,  Long  Lake,  Great  Bend,  Cheyenne  River,  etc.,  Nebraska.  — 
Fort  Harker,  Fort  Hayes,  Fort  Wallace,  Kansas.  —  Fort  Lyon,  Santa  Fe, 
New  Mexico. 

Eocene.  —  Everywhere  in  Tippah  County  ;  Yockeney  River  ;  New  Pros- 
pect P.  0.,  Winston  County  ;  Marion,  Lauderdale  County ;  Enterprise, 
Clarke  County  ;  Jackson,  Satartia,  Yazoo  County ;  Homewood,  Scott  County  ; 
Chickasawhay  River,  Clarke  County  ;  Winchester,  Red  Bluff  Station,  Wayne 
County ;  Vicksburg,  Amsterdam,  Brownsville,  Warren  County ;  Brandon, 
Byram  Station,  Rankin  County ;  Paulding,  Jasper  County,  Miss.  —  Clai- 
borne,  Monroe  County  ;  St.  Stephen's,  Washington  County,  Ala.  —  Charles- 
ton, S.  C.  —  Tampa  Bay,  Florida.  —  Fort  Washington,  Fort  Marlborough, 
Piscataway,  Md.  —  Marlbourne,  Va.  —  Brandon,  Vt.  —  In  New  Jersey,  at 
Farmingdale,  Squankum  and  Shark  River,  Monmouth  Co.  —  Green  River, 
Fort  Bridger,  Wyoming.  —  Canada  de  las  Uvas,  Cal. 

Miocene.  —  Gay  Head,  Martha's  Vineyard,  Mass.  —  Shiloh,  Jericho, 
Cumberland  County,  and  Deal,  Monmouth  County,  N.  J.  —  St.  Mary's,  Eas- 
ton,  Md.  —  Yorktown,  Suffolk,  Smithfield,  Richmond,  Petersburg,  Va.  — 
Astoria,  Willamette  Valley,  John  Day  Valley,  Oregon.  —  San  Pablo  Bay, 
Ocoya  Creek,  San  Diego,  Monterey,  San  Joaquin  and  Tulare  Valleys,  Cal.  — 
White  River,  Upper  Missouri  Region.  —  Crow  Creek,  Colorado. 

Pliocene.  —  Ashley  and  Santee  Rivers,  Si  C.  —  Platte  and  Niobrara 
Rivers,  Upper  Missouri.  —  John  Day  Valley,  Oregon.  —  Sinker  Creek, 
Idaho.  —  Alameda  County,  Cal. 


350  APPENDIX. 


B.  —  Geological  Implements,  Specimens,  etc. 

1.  Implements.  —  The  student  requires  for  his  geological  excur- 
sions and  research  the  following  implements  :  — 

(1.)   A.  hammer.     If  his  object  is  to  get  specimens  of  hard  rocks,  or  obtain 
minerals  from  such  rocks,  it  should  have  the  form  in  Fig.  406,  the  edge  being 
in  the  direction  of  the  handle.     But  if  fossils  are  to  be  collected, 
this  edge  should  be  transverse  to  the  handle.     The  face  should      FiS*  406. 
be  flat,  and  nearly  square,  with  its  edges  sharp  instead  of  rounded. 
The  socket  for  the  handle  should  be  large,  that  the  handle  may 
be  strong.     The  hammer,  for  ordinary  excursions,  should  weigh 
1^  pounds  exclusive  of  the  handle  ;  the  handle  should  be  about 
12  inches  long.     Another  is  required  for  trimming  specimens, 
weighing  half  a  pound. 

(2.)  A  steel  chisel,  6  inches  long,  such  as  is  used  by  stone- 
cutters.    Also,  another  half  this  size. 

(3.)  A  clinometer,  with  magnetic  needle  attached.     The  best 
kind  is  a  clinometer-compass  3  inches  in  diameter,  having  a 
square  base  about  3^  inches  each  side,  two  sides  of  the  base  being  parallel  to  the 
north  and  south  line  of  the  compass. 

(4.)  A  small  magnet.  A  magnetized  blade  of  a  pocket-knife  is  a  good 
substitute. 

(5.)  A  measuring-tape  50  feet  long.  The  field  geologist  should  know  ac- 
curately the  measurements  of  his  own  body,  his  height,  length  of  limbs,  step 
or  pace,  that  he  may  use  himself,  whenever  needed,  as  a  measuring-rod. 

(6. )  In  many  cases,  a  pick,  a  crow-bar,  a  sledge-hammer  of  4  to  8  pounds' 
weight,  and  the  means  of  blasting,  are  necessary. 

(7.)  Besides  the  above,  a  barometer  and  surveyor's  instruments  are  occa- 
sionally required.  Of  the  latter,  a  hand-level  is  a  desirable  instrument  for 
determining  small  elevations  by  levelling  ;  it  is  a  simple  brass  tube,  with 
cross-hairs,  bubble,  and  mirror.  A  first-rate  aneroid  barometer  is  excellent 
for  all  heights  between  5  feet  and  2,000  feet ;  and,  having  one,  the  hand- 
level  is  superfluous. 

2.  Specimens.  —  Specimens  for  illustrating  the  kinds  of  rocks 
should  be  carefully  trimmed  by  chipping  to  a  uniform  size,  pre- 
viously determined  upon  :  3  inches  by  4  across,  and  1  inch  through, 
is  the  size  commonly  adopted.     In  the  best  collections  of  rocks,  the 
angles  are  squared  and  the  edges  made  straight  with  great  precision. 
They  should  have  a  fresh  surface  of  fracture,  with  no  bruises  by 
the  hammer.     It  is   often  well  to   leave  one  side  in  its  natural 
weathered  state,  to  show  the  eifects  of  weathering. 

Specimens  of  fossils  will,  of  course,  vary  in  size  with  the  nature 


APPENDIX.  351 

of  the  fossil.  When  possible,  the  fossil  should  be  separated  from 
the  rock ;  but  this  must  be  done  with  precaution,  lest  it  be  broken 
in  the  process;  it  should  not  be  attempted  unless  the  chances  are 
strongly  in  favor  of  securing  the  specimen  entire.  The  skilful  use 
of  a  small  chisel  and  hammer  will  often  expose  to  view  nearly  all 
of  a  fossil  when  it  is  not  best  wholly  to  detach  it.  "When  the 
fossils  in  a  limestone  are  silicified  (a  fact  easily  proved  by  their 
scratching  glass  readily  and  their  undergoing  no  change  in  heated 
acid),  they  may  be  cleaned  by  putting  them  into  an  acid,  and  also 
applying  heat  very  gently,  if  effervescence  does  not  take  place 
without  it.  The  best  acid  is  chlorohydric  (muriatic)  diluted  one 
half  with  water. 

Collections  both  of  rocks  and  fossils  should  always  be  made  from 
rocks  in  place,  and  not  from  stray  bowlders  of  uncertain  origin. 

3.  Packing.  —  For  packing,  each  specimen  should  be  enveloped 
separately  in  two  or  three  thicknesses  of  strong  wrapping-paper. 
This  is  best  done  by  cutting  the  paper  of  such  a  size  that  when 
folded  around  the  specimen  the  ends  will  project  two  inches  (more 
or  less,  according  to  the  size  of  the  specimen) ;  after  folding  the 
paper  around  it,  turn  in  the  projecting  ends  (as  the  end  of  the  finger 
of  a  glove  may  be  turned  in),  and  the  envelope  will  need  no  other 
securing.     Pack  in  a  strong  box,  pressing  each  specimen,  after  thus 
enveloping  it,  firmly  into  its  place,  crowding  wads  of  paper  between 
them  wherever  possible,  and  make  the  box  absolutely  full  to  the 
very  top  (by  packing-material  if  the  specimens  do  not  suffice),  so 
that  no  amount  of  rough  usage  by  wagon  or  cars  on  a  journey  of  a 
thousand  miles  would  cause  the  least  movement  inside. 

4.  Labelling.  —  A  label  should  be  put  inside  of  each  envelope, 
separated  from  the  specimen  by  a  thickness  or  more  of  the  paper. 
The  label  should  give  the  precise  locality  of  the  specimen,  and  the 
particular  stratum  from  which  taken,  if  there  is  a  series  of  strata  at 
the  place ;  it  should  also  have  a  number  on  it  corresponding  to  a 
number  in  a  note-book,  where  fuller  notes  of  each  are  kept,  together 
with  the  details  of  stratification,  strike,  and  dip,  sections,  plans, 
changes  or  variations  in  the  rocks,  and  all  geological  observations 
that  may  be  made  in  the  region.     A  specimen  of  rock  or  fossil  of 
unknown  or  uncertain  locality  is  of  very  little  value. 


352  APPENDIX. 

5.  Note-Book.  —  The  note-book  should  have  a  stiff  leather  cover, 
and  be  made  of  rather  thick,  smooth  writing-paper,  good  for  sketch- 
ing as  well  as  for  writing.  Five  inches  by  three  and  a  half  is  a 
convenient  size.  A  kind  made  of  prepared  paper,  and  provided 
with  a  zinc-pointed  pencil,  is  often  sold  for  the  purpose,  and  is 
excellent  until  it  gets  perchance  a  fall  into  the  water,  when  the 
notes  that  may  have  been  carefully  made  will  be  pretty  surely 
obliterated.  If  the  geologist  is  a  draughtsman,  he  may  also  need  a 
portfolio  for  carrying  larger  paper ;  but  the  small  note-book  will,  in 
general,  answer  every  purpose. 


INDEX. 


NOTE  —  The  asterisk  after  the  number  of  a  page  indicates  that  the  subject  referred  to  is 
illustrated  by  a  figure. 


Acadian  group,  80. 
Acalephs,  57,*  58. 
Acanthoteuthis,  172.* 
Acephals,  56.* 
Acrodus  minimus,  52.* 

nobilis,  52.* 
Acrogens ,  60. 

Carboniferous,  125. 

Devonian,  106. 
Actinia,  57.* 
Actinocrinus      proboscidialis, 

129.* 

.SSpyornis,  extinction  of,  243. 
Ages  in  Geology,  64,  65. 
Alabama  period,  203,  204. 
Albite,  16. 
Algse,  60. 

Alleghany  coal-area,  115. 
Alluvial  deposits,  226,  283 
Alps,  glaciers  in,  300. 
America,  North,  Geography  of. 

See  GEOGRAPHY. 
Ammonites,  170.* 

Huniphreysianus,  170.* 

Jason,  170.* 

placenta,  191.* 

tornatus,  171  * 

ofMesozoic,  198. 
Amphibians,  50, 165,*  174.* 
Amphipods,  54  * 
Aiuphitherium,  179  * 
Amygdaloid,  318. 
Anatifa,  54.* 
Anchitherium,213.* 
Andalusite,  17.* 
Angiosperms,  62. 

Cretaceous,  186.* 

Tertiary,  206.* 
Animal  kingdom,  47,  48. 
Anisopus,  tracks  of,  166.* 
Anogens,  60. 
Ant-eaters,  216. 
Anthracite,  18,  121. 

origin  of,  156. 

vegetable  tissues  in,  134.* 
Anticlinal,  42.* 
Anticlinorium,  338. 
Appalachian  revolution,  155. 


Appalachians,    formation    of, 
151,248,334 

folded  rocks  of,  152.* 

thickness  of  formations  of, 

104,  151. 
Araucariae ,  62. 
Archaean  time,  65,  73. 

N.  America,  73  * 
Archaeoniscus  Brodiei,  173.* 
Archaeopteryx,  178. 
Archimedes  reversa,  129  * 
Arctic  coal  area,  117. 
Arenicola  piscatorum,  54.* 
Argillyte,  24. 
Artesian  wells,  285.* 
Arthrolycosa,  130.* 
Articulates,  49,  53,*  81.* 
Asaphus  gigas,  88.* 
Ascidians,  54. 
Astarte  Conradi,  208  * 
Athyris  subtilita,  129.* 
Atmosphere,  agency  of,  273. 
Atolls,  269.* 
Atrypa  aspera,  110.* 
Auk,  extinction  of,  243 
Aulopora  cornuta,  109.* 
Australia,  basaltic  columns  of, 
319.* 

Marsupials  of,  in  Quater- 
nary, 230. 
Avicula  emacerata,  96.* 

Trentonensis,  88.* 
Azoic.     See  ARCELEAN. 

Baculites  ovatus,  191.* 

Bagshot  beds,  206. 

Bala  formation,  86. 

Basalt,  26,  311. 

Basaltic  columns,  35,*  319.* 

Bathygnathus  borealis,  166.* 

Beach-formations,  32,  292. 

Bear,  cave,  233. 

Beetles,  130. 

Belemnitella  mucronata,  191.* 

Belemnites,171,*191.* 

Belodon  priscus,  166.* 

Bembridge  beds,  206. 

Bernese  Alps,  296. 


Bilin,  infusorial  bed  of,  208. 
Birds,  50. 

Cretaceous,  194. 

of    Connecticut     Valley, 
167* 

ofSolenhofen,178,  201. 

Tertiary,  210. 
Birdseye  limestone,  85 
Bituminous  coal,  18,  121. 
Black  River  limestone,  85. 
Black  slate  of  Devonian,  104. 
Bore,  289. 

Bowlders,  220,  221,  282,  298. 
Brachiopods,    56  *    88*   96  * 

98,*  129.* 

Brandon  fossil  fruits,  206.* 
Breccia,  23. 
Brown  coal,  18. 
Bryozoans,  57.* 
Buhrstone.  Tertiary,  205. 
Bunter  Sandstein,  166. 
Buprestis,  173.* 

Catamites,  107, 125.* 

in  Triassic,  167. 
Calamopsis  Dana-,  207  * 
Calcareous  rocks,  22,  25. 
Calciferous  sand-rock,  85. 
Calcite,  19.* 
Callista  Sayana,  209  * 
Callocystites  Jewettii,  57  * 
Calymene  Blumenbachii,  54  * 

89. 

Cambrian,  81. 

Camel,  Tertiary  American, 214. 
Canadian  period,  84. 
Cancer,  54.* 
Canons,  278.* 
Caradoc  sandstone,  86. 
Carbon,  18. 
Carbonate  of  lime,  19. 
Carbonic  acid,  18. 
Carboniferous  age,  114. 
Carcharodon  angustidens,52.* 

megalodon,  209. 
Cardita  planicosta,  208.* 
Caryocrinus  ornatus,  96  * 
Catbpterus  gracilis,  165.* 

W 


354 


INDEX. 


Catskill  period,  105. 

Connecticut   River   sandstone 

Dikes,  30,*  318 

Cauda-galli  grit,  103. 

and  footprints,  159. 

Dicotyledons,  62. 

Cave  animals  of  Quaternary, 

terraces,  227.* 

Dinoceras,  213.* 

233. 
Cenozoic  time,  201. 

trap  rocks,  160. 
Continents,    basin-like    shape 

Dinornis,  extinction  of,  242. 
Dinosaurs,  176,210. 

general   observations   on, 

of,  9.* 

Dinothere,  215.* 

243. 

origin  of,  330.* 

Dioryte,  26. 

Cephalaspis,  112.* 

Contraction  a  cause  of  change 

Dip,  40.* 

Cephalates,  55.* 

of  level,  327. 

D.protodon,236. 

Cephalization,     progress     in, 

Coprolites,  177. 

Dipterus,  112.* 

258. 

Coral  islands,  268.* 

Discina,  252. 

Cephalopods,  55.* 
ofMesozoic,200. 
Cestracionts,  52,*  113,  173. 

reef  of  the  Devonian,  103. 
Corals,  formation  of,  58. 
recent,  57.* 

Dislocated  strata,  39.* 
Dodo,  extinction  of,  241. 
Doleryte,  26,  317. 

Chsetetes  lycoperdon,  87.* 

Coralline  crag,  206. 

Dolomite,  19. 

Chain-coral,  9ti.* 

Corniferous  limestone,  103. 

Drift,  220. 

Chaik,  185,  195. 

period,  103. 

sands,  32,*  274. 

Champlain  period,  220,  225. 

Crabs,  53.* 

scratches,  221.* 

Chazy  limestone,  85. 
Cheirolepis  Traillii,  51. 

Crassateila  alta,  208.* 
Craters,  307. 

Dromatherium  sylvestre,  1G8.* 
Dudley  limestone,  95. 

Cheirotherium,  174.* 

Crepidula  costata,  209.* 

Dunes,  274. 

Chemung  period,  1U4. 
Chlorite  slate,  24. 

Cretaceous  period,  159,  184. 
America,  map  of,  194. 

Dynamical  Geology,  264. 

Chonetes  mesoloba,  129.* 

Crevasses,  296. 

Eagre,  289. 

setigera,  110.* 
Cidaris  Blumenbachii,  168.* 

Crinoidal    limestone,    Subcar- 
boniferous,  119. 

Earth,  size  and  features  of,  5. 
relation  to  Man,  343. 

Cinders,  308. 

Crinoids,  58.* 

features,  origin  of,  327. 

Cinnamomum,  Tertiary,  207.* 

Jurassic,  168.* 

interior  of,  328. 

Circumdenudation,  279. 

Primordial.  82.* 

Earthquakes,  origin    of,  327, 

Clathropteris,  163.* 

Silurian,  88,*  97.* 

329. 

Clay,  20. 

Subcarboniferous,  128.* 

Ebb-and-flow  structure,  32. 

Clay  -slate,  24. 

Crocodiles,  193. 

Echini,  57.* 

Cleavage,  slaty,  36.* 

Crustaceans,  53.* 

Mesozoic,  174.* 

Cliff-limestone,  104. 

Cryptogams,  60. 

Echinoderms,  57.* 

Climate,  cause  of  changes  in, 

Crystalline  rocks,  20. 

Edentates,  Quaternary,  235.* 

330. 

Crystallization.    See  METAMOR- 

Elephants,    Quaternary,   234, 

Carboniferous,  136. 

PHISH. 

235. 

Cretaceous,  195. 

Ctenacanthus  major,  131.* 

Tertiary,  215. 

Jurassic,  183. 
Paleozoic,  147. 

Ctenoids,  50.* 
Currents,  oceanic,  289,  290. 

Elephas  primigenius,  234,  239.*- 
Eievation  of  coast  of  Sweden, 

Quaternary,  237. 

Cyathophylloid  corals,  58,  87  * 

232. 

Tertiary,  219. 

96,*  109.* 

of  Green  Mountains,  90. 

Clinkstone.     See  PHONOLYTE. 

Cyathophy  Hum          rugosum  , 

of  Himalayas,  218. 

Clinometer,  40.* 

109.* 

of  Rocky  Mountains,  217. 

Clinton  group,  93. 

Cycads,  62. 

of  Western  South  America, 

Coal,  kinds  of,  18. 

Triassic  and  Jurassic  ,162.* 

219. 

formation  of,  133. 

Cycloids,  50. 

of  Quaternary  ,  216. 

deprived  of  bitumen,  155. 
Coal-areas  of  Britain  and  Eu- 

Cyclonema  cancellata,  96.* 
Cyclopteris  linnaeifolia,  163.* 

Elevations,  causes  of,  327. 
Emery,  15. 

rope,  117.* 
-areas  of  N.  America,  115.* 

Halliana,  106. 
Cypris,  53. 

193. 

-beds,  characters  of,  120. 

Cystideans,58,*97. 

Encrinus  liliiformis,57,*  168.* 

-beds,  formation  of,  135. 

Cythere  Americana,  54.* 

Endogens,  63 

-beds  of  Triassic,  164. 

England,   geological  map    of, 

-beds,  flexures  in,  152.* 

Decapods,  53.* 

118.* 

-formation,  rocks  of,  119. 

Delta  of  Mississippi,  283.* 

Entomostracans,  53.* 

-plants  of  Richmond,  1*59.* 

Deltas,  284. 

Eocene,  202. 

-plants  of  the  Carbonifer- 

Dendrophyllia, 57.* 

Eosaurus  Acadianus,  132  * 

ous,  123.* 
Coccoliths,  61. 

Denudation,  43,*  276,  280. 
Desmids,  61,*  108.* 

Eoscorpius  carbonarius,  130.* 
Kozoon,  77.* 

Coccosteus,  111.* 

Detritus,  282. 

Ephemera,  165- 

Cockroaches,  130. 

Devonian  age,  103. 

Equiseta,  60,  107,  127. 

Coin-conglomerate,  240.* 

hornstone,  microscopic  or- 

Equivalent strata,  44. 

Colorado,  canon  of,  278.* 

ganisms  in,  108.* 

Erie  shale,  104. 

Columnaria  alveolata,  87-* 

Diabasyte,  26,  27,  318,*  326. 

Erosion  by  rivers,  275^286. 

Comatulids,  58. 

Diamond,  18. 

over  continents,  279.* 

Comprehensive  types,  253. 

Diatoms,  61.* 

Eruptions  of  volcanoes,  309. 

Concretions,  34,  35.* 

in  hornstone,  108  * 

non-volcanic,  317. 

Conformable  strata,  43.* 

formation  of  deposits  by, 

Estheria  ovata,  164.* 

Conglomerate,  23. 

186. 

Estuary  formations.  2S4 

Conifers,  62,  107,  127. 

Tertiary,  207. 

Euplectella  speciosa,  188.* 

INDEX. 


355 


Eurypterus  remipes,  98.* 
Exogyra  arietina,  ly>  * 
Extermination  of  species,  92, 

147,200,241. 
methods  of,  265. 

Fagus,207.* 
Fan-palm,  206. 

Fasciolaria  buccinoides,  191.* 
Faults,  41,*  153.* 
Favosites  Goldfussi,  109.* 

Niagarensis,  96.* 
Feldspar,  16. 
Ferns,  60. 

Devonian,  106.* 

Carboniferous,  125.* 
Fiords,  223. 
Fishes,  50  * 

Age  of,  103. 

Carboniferous,  130.* 

Devonian,  111.* 

Mesozoic,  173,*  192.* 

Silurian,  98. 

Teliost,  191, 192.* 
Fish-spines,  113,*  131  * 
Flags,  22. 
Flint,  14,  186. 
Flint  arrow-heads,  238. 
Flow-and-plunge       structure, 

32,*  293. 

Fluvio-marine  formations,  292 
Folded  rocks, 42,*  74, 153,* 327. 
Footprints.     See  TRACKS. 
Foraminifera,  60.* 
Formation,  29. 

Fossils,  use  of,  in  determining 
the  equivalency  of  stra- 
ta, 3,  46. 

list  of  localities  of,  346. 

number  of  species  of,  102, 

253. 

Fragmental  rocks,  20,  22. 
Freestone  of  Portland,  Ct.,  159. 
Fresh  waters,  action  of,  275. 
Fruits,  Carboniferous,  127.* 

Tertiary,  206.* 
Fusulina,  59.* 
Fusus  Newberryi,  193.* 

Ganoids,  50,  51  * 

Carboniferous,  131.* 

Devonian,  111.* 

Triassic,  165.* 
Garnet,  17  * 
Gasteropods,  56.* 
Geanticlinal,  42,  329. 
Genera,  long-lived,  149. 
Genesee  shale,  104. 
Genesis,  263. 
Geode,  35. 

Geography,  progress  in  North 
America,  77,  78,  146, 
246,  332. 

American,    in    Archaean, 
73,*  77, 143- 

in  Carboniferous,  137. 

in  Cretaceous,  194  * 

in  Devonian,  113. 

in  Mesozoic,  196. 

in  Paleozoic,  144. 

in  Quaternary,  243. 


Geography.  American,  in  Silu- 
rian, 89,  98. 

in  Tertiary,  216.* 

Triassic,  180. 
Geosynclinal,42,  329. 
Geysers,  316.* 
Giants'  Causeway,  319. 
Gilbert  Islands,  270. 
Glacial  period,  219,  220,  230. 
Glacier,  great,  of  Switzerland, 
296.* 

scratches,  222.* 

theory  of  the  drift,  223. 
Glaciers,  295. 

Glen  Roy,  benches  of,  229. 
Globigerina,  58.* 
Glyptodon,  236.* 
Gneiss,  23. 
Goniatites,  first  of,  109. 

last  of,  in  Triassic,  170. 

Marcellensis,  110.* 
Grammy  sia       Hamiltonensis, 
112.* 

bisulcata,  110.* 
Granite,  23,  26. 
Graphite,  18,76. 
Graptolites,  87.* 
Greenland,  glaciers  of,  300. 

changes  of  level  in,  232. 
Green  Mountains,  emergence 
of,  90. 

limestone  of,  85. 
Green-sand,  185. 
Grit,  23. 

Gryph8ea,speciesof,169,*190  * 
Guadaloupe,  human  skeleton 

of,  240.* 

Gulf  of  Mexico,  progress  of,  216. 
Gymnosperms,  62. 
Gypsiferous  formation,  160. 
Gypsum,  94,  123. 
Gyrodus  umbilicus,  51.* 

Halysites  catenulata,  96.* 
Hamilton  period,  104 
Harmony  in  the  life  of  an  age, 

254. 

Hawaii,  volcanoes  of,  309.* 
Heat,  303,  329. 

evidence  of  internal,  303 
Height  of  Aconcagua  peak ,  307  • 

of  Sorata,  307. 

of  Shasta,  307. 
Hempstead  beds,  206. 
Herculaneum,  314. 
Heterocercal,  51  * 
Hipparion,  213.* 
Hitchcock ,  E. ,  tracks  described 

by,  166.* 

Holoptychius,  112.* 
Homalonotus,  93.* 
Homocercal,  51 
Hornblende,  1(3 
Hornblende  rocks,  24. 
Hornstone,  103. 

microscopic   remains    in , 

108.* 

Horse,  fossil,  212,  213.* 
Hot  Springs,  316. 
Hudson  Bay,  332. 
Hudson  River  shale,  86. 


Hyaena  spelaea,  233. 
Hybodus,  species  of,  52.* 
Hydroid  Acalephs,  58.* 
Hydromica  slate,  24. 
Hyposyenyte,  24,  26. 

Ice  of  lakes  and  rivers,  295. 

glacier.  295. 
Icebergs,  223,  295,  300. 
Ichthyosaurus,  175.* 
Igneous  rocks,  21, 26,306,340. 

ejections  of  Lake  Superior 
region,  90 

ejections,  Triassic,  160. 
Iguanodon,176, 195. 
Infusorial  beds,  Tertiary,  208. 
Ink-bag,  fossil,  172.* 
Inoceramus       problematicus, 

190,*  209. 
Insects,  53. 

first  of,  111. 

Carboniferous,  130.* 

Jurassic,  173.* 

Triassic.  164.* 
Irish  Deer,  234. 
Iron  ore,  Archaean,  74.* 
Iron  ores,  Carboniferous,  120. 
Iron  mountains  of  Missouri,  74, 
Isopods,  54.* 
Itacolumyte,  25. 

Joints  in  rocks,  35,  36,*  329. 
Jurassic  period,  159. 

Kerosene,  122. 
Keuper,  161. 
Keweenaw  Point,  85,  90. 
Kilauea,  310. 
Kingsmill  Islands,  270. 
Kirkdale  cavern,  233. 

Labradorite,  16. 

Labyrinthodonts,  174.* 

Lacustrine  deposits,  228. 

Lake   Champlain   in   Quater- 
nary, 228. 

Mem  phremagog,  Devonian 
coral-reef  of,  104. 

Lakes,origin  of  Great,  146, 247. 
Lake-dwellings,  240. 

Lamellibranchs,  56.* 

Laminated  structure,  22,  31.* 

Lamna  elegans,  52,*  210. 

Land-slides,  286. 

Lava,  27,308. 

Layer,  29. 

Lecanocrinus  elegans,  88.* 

Leguminosites,  187.* 

Leperditia  alta,  98.* 

Lepidodendra,  97. 

Lepidodendron        aculeatum, 

125.* 
primajvum,  106.* 

Lepidosteus  osseus,  51.* 

Leptasna  sericea,  88  * 
transversalis,  96  * 

Leptgenas,  last  of,  169. 

Lesley,  results  of  denudation, 
279.* 

Level,  change  of,  in  Greenland, 
232. 


356 


INDEX. 


Level,  changes  of,  in  the  Qua- 
ternary, 228,  230,  231. 
origin  of  changes  of,  327. 

Level.     See  ELEVATION. 

Lias,  161. 

Libellula,  173  * 

Life,  agency  of,  in  rock-mak- 
ing, 264. 
general   laws  of  progress 
of,  251 

Life.     See  SPECIES. 

Lignite,  18,  185,  219. 

L  gnitic  period,  202,  204. 

Limestone,  25,  26. 

formation  of,  143, 265, 268, 
297. 

Limestones  of  Mississippi  Val- 
ley, 141  * 

Limulus,53. 

Lingulse,  81,*  252. 

Lingula  flags,  80. 

Liriodendron  Meekii,  187.* 

Lithostrotion  Canadense,  129.* 

Llandeilo  flags,  86. 

Llandovery  beds,  95. 

Localities  of  fossils,  list  of,  346. 

Locusts,  130. 

London  clay,  206. 

Lorraine  shale,  86. 

Lower  Helderberg,  94. 

Ludlow  group,  95. 

Lycopods,  60,  97, 106,*  126.* 

Macluerodus,  234. 
Madagascar,  /Epyornis  of,  243. 
Magnesian  limestone,  19, 25, 85. 
Magnolia,  206. 
Mammals,  50. 

Age  of,  202. 

first  of,  168.* 

Jurassic,  179,*  201. 

Tertiary,  210  * 

Triassic,  168,*  179 
Man,  Age  of,  201,  219,  238. 

fossil,  of  Guadaloupe,  240.* 

the  head  of  the  system  of 

life,  241,  257. 

Map  of  Pennsylvania  coal  re- 
gion, 116.* 

of  England,  118.* 

of  N.  America,  Archaean, 
73.* 

of  N.  America,  Cretaceous, 
194. 

of  N    America,   Tertiary, 
216* 

of  New  York  and  Canada, 
71.* 

of  United  States,  69.* 
Marble,  26. 

of  Green  Mountains ,  85 , 91. 
Marcellus  shale,  104 
Marine  formations,  291.      > 
Marl,  22, 185. 
Marlyte,  23. 
Marsupials,  50. 

Triassic,  168, 179. 

Jurassic,  179.* 
Massive  structure,  22,  31.* 
Mastodon,  QuaVrnary,  234.* 

Tertiary,  215. 


Mastodonsaurus,  174  * 
Mauna.     See  MOUM. 
May-flies,  130.* 
Medina  group,  93. 
Medusa;,  57,*  58. 
Megaceros  Hibernicus,  234. 
Megalosaur,  176.* 
Megathere,  235.* 
Mer-de-glace,  296. 
Mesozoic  time,  157. 

general    observations  on, 
193. 

geography  of,  196. 

life  of,  198. 

Metamorphic  rocks,  21,  23. 
Metamorphism,     nature     and 

cause  of,  319,  337. 
Miamia  Bronsoni,  130.* 
Mica,  16. 

schist,  24. 

Michigan  coal-area,  115 
Microdon  bellistriatus,  110  * 
Microscopic    organisms,    59,* 

61,*  108,*  267. 
Millepores,  58. 
Mineral  coal.     See  COAL. 

oil,  122. 
Miocene,  202 

Mississippi  River,  amount  of 
water  of,  276. 

delta  of,  283.* 

detritus  of,  282. 
Moa,  extinction  of,  242. 
Mollusks,  49,  54.* 
Monadnock,  221. 
Monoclinal,  42. 
Monocotyledons,  63. 
Moraines,  298.* 
Mosasaur,  192,*  193.* 
Mountains,  making  of,  216, 327. 

of  Paleozoic  origin,  145 

made  after  the  close  of  the 
Paleozoic,  150. 

made  after  the  Jurassic, 
183 

made  during  the  Tertiary, 
216. 

See  ELEVATIONS. 
Mount  Blanc,  300. 

Holyoke,  160,  318. 

Loa,  309.* 

Tom,  318. 
Muck,  266. 
Mud-cones,  316. 
Mud-cracks,  33  * 
Muschelkalk,  161. 
Myriapods,  53, 130. 

Nautilus,  55  * 

in  the  Silurian,  89. 
Nautilus  tribe,  number  of  ex- 
tinct species  of,  253. 
Neolithic  era,  239. 
New  Brunswick  coal-area,  115. 
New  Caledonia  reefs,  272. 
New  South  Wales  cliff,  287.* 
Niagara  Falls ,  rocks  of,  28  *  94.* 

group,  93. 

River,  gorge  of,  245.  279. 
Noeggerathij,        See    CYCI/>P- 
T^RIS. 


North  America,  form  of,  9. 
geography  of.     See  GEOG- 
RAPHY. 

Norwich  crag,  206. 
Notidanus  primigenius,  52.* 
Nototherium,  236. 
Nova  Scotia  coal-area,  115. 
Nummulites,  59.* 
Nummulitic  limestone,  205. 
Nullipores,  61. 
Nuts,  fossil,  127,  206. 

Oak,  206. 

Ocean,  depression  of,  6,  7. 

effects  of,  286. 

Oceanic  basin,  origin  of,  331. 
Ohio,  coral-reef  of  Falls  of,  1 J4. 
Oil,  mineral,  122. 
Old  red  sandstone,  105. 
Oneida  conglomerate,  93. 
Onondaga  limestone,  103. 
Oolitic  structure,  25. 
Ooiyte,  161. 

Orbitolina  Texana,  189.* 
Oreodon  gracilis,  215.* 
Orient,  characteristics  of,  5. 
Origin  of  species,  263. 
Oriskany  period,  93,  95. 
Orohippus,  212. 
Orthis  biloba,  96.* 

occidentalis,  88.* 

testudinaria,  88  * 
Orthoceras  junceum,  88.* 

last  of,  175,  200. 
Orthoclase,  15. 

Osmeroides  Lewesiensis,  192.* 
Ostracoids,  54.* 

of  Triassic,  164.* 
Ostrea  sellgeformis,  208.* 
Otozoum  Moodii,  166. 
Outcrop,  40.* 
Ox,  first  of,  216. 
Oyster,  Tertiary,  209.* 

Palaeaster  Niagarensis,  57.* 
Palaeoniscus  lepidurus,  51.* 

Freieslebeni,  51,*  131.* 
Paleolithic  era,  238. 
Paleothere,  211  * 
Paleozoic  time,  78. 

disturbances  closing,  150. 

general   observations  on, 

140. 

Palephemera  mediseva,  165.* 
Palisades,  160 
Palms,  first  of.  186. 

Tertiary,  207.* 
Palpipes  priscus,  173  * 
Paludina  Fluviorum,  1^9  * 
Paradoxides  HarlanS  82.* 
Paris  basin,  Tertiary  animals 

of,  211. 
Paumo  u  Archipelago,  271. 
Peat,  formation  of,  265. 
Peccary,  fossil,  214. 
Pecopteris         Stuttgartensis, 

163.* 

Pemphix  Sueurii,  173  * 
Pentamerus  galeatus,  98.* 

oblongus,  96.* 
Peutremites,  128.* 


INDEX. 


357 


Peridotyte,  26,  318. 

Rhinoceroses,  Tertiary,  214.*, 

Permian  period,  115,  123. 

Quaternary,  234. 

Petraia  corniculum,  88.* 

Rhizopods,  59.* 

Petroleum,  122. 

Cretaceous,  187.* 

Phacops  bufo,  110  * 

formation  of  deposits  by, 

Pbascolotherium,  178.* 

267. 

Phenogams,  62. 

Rhode  Island  coal-area,  115. 

Phonolyte,  326. 
Physiographic  Geology,  6. 
Pictured  rocks,  85.      ' 

Rhynchonella  cuneata,  96.* 
ventricosa,  98.* 
Rill-marks,  33,*  293. 

Plants,  47,  60. 

Ripple-marks,  33,*  293. 

Carboniferous,  123.* 

Rivers,  action  of,  275. 

Cretaceous,  187.* 

of  Paleozoic  origin  ,  146. 

earliest  marine,  76,  81. 

River  terraces,  227,*  230.* 

Devonian,  99,*  106.* 
Tertiary,  207.* 

Roches  moutonnees,  299. 
Rock,  definition  of,  13 

Triassic,  162.* 

Rocks,  constituents  of,  14. 

Platephemera  antiqua,  111.* 
Platyceras  angulatum,  96.* 
Plesiosaurs,  175,*  193. 
Pleurotomaria       lenticularis, 

formation  of  sedimentary. 
275. 
fragmental  ,  20. 
kinds  of,  20. 

88.* 

metamorphic,  21. 

tabulata,  129.* 
Pliocene,  202. 

of  Mississippi  Valley,  sec- 
tion of,  141  * 

Pliosaur,  176. 

origin  of  Archaean  ,  75. 

Podozamites  lanceolatus,  163  * 

origin  of  Paleozoic,  142. 

Polycystines,  59*  263. 

thickness  of  Paleozoic   in 

Polyps,  58.* 

North  America,  140,  249. 

Polythalamia.      See    FORAM.- 

Rocky  Mountains,  origin  of, 

NIFERA. 

196,217,334. 

Pompeii,  314. 

Mountain  coal-area,  204. 

Porphyry,  27,  308. 

Rotalia,  59.* 

Portland  (England)  dirt-  bed, 

161. 

Sabal,  206. 

(Connecticut)      freestone, 

St.  Lawrence  River  in  the  Qua- 

159. 

ternary,  228. 

Potsdam  sandstone,  80. 

St.  Peter's  sandstone,  85. 

Primordial  period,  80. 

Saliferous    group    of   Britain 

Prionastraea  oblonga,  168.* 

and  Europe.  161. 

Productus  Nebrascensis,  129.* 

rocks  of  New  York,  94. 

Protophytes,  61.* 

Salina  rocks,  94,  100. 

Protozoans,  49,  59  *  187. 

Salisbury  Craigs,  318. 

Pterichthys,  111.* 

Salix  Meekii,  187.* 

Pterodactyl,  177,*  193. 

Salt  of  coal  formation,  122. 

Pterophyllum,  163.* 

of  Salina,  etc,  94. 

Pteropods,  56.* 

of  Triassic,  161. 

Pterosaurs,  177,*  193. 

Sand,  20. 

Ptilodictya,  88.* 

Sand-banks,  291,  293. 

Pudding-stone,  22. 

Sand-scratches,  274. 

Pupa  vetusta,  129.* 

Sandstones,  22. 

Pyrifusus,  191  * 

Sapphire,  15. 

Pyroxene,  16. 

Sassafras  Cretaceum,  187.* 

Sauropus  primaevus,  132  * 

Quadrupeds.     See  MAMMAL. 

Scaphites  larvscformis,  191.* 

Quaternary,  201,  219,  237. 

Schist,  schistose  rocks,  22. 

Quartz,  14.* 

Schoharie  grit,  103. 

Quartz  rock,  or  Quartzyte,  24. 

Scolithus  linearis,  82. 

Quebec  group,  85. 

Scoria,  27. 

Quercus,  Tertiary,  207.* 

Scorpions,  first  of,  130.* 

Sea-beaches,  elevated,  228. 

Radiates,  49,  57.* 

Sea-weeds,  60. 

Rain-prints,  34,*  145. 

Section  of  New  York  rocks,  72  * 

Raniceps  Lyellii,  132.* 

of  the  series  of  rocks,  67.* 

Rays,  52. 

Sections   of   Paleozoic    rocks, 

Reefs,  coral,  268.* 

105,*  141,*  153.* 

Regelation,  298 

Sedimentarv  beds,   formation 

Reindeer  era,  231,238. 

of,  301. 

Reptiles,  50. 

Selachians,  52  * 

Mesozoic,  165,*  174  *  192  * 

Devonian,  113.* 

201. 

Serolis,  54.* 

Reptilian  age,  158. 

Serpentine,  18. 

Shale,  22,  23,  31. 
Sharks,  52  * 

Devonian,  113* 

Teeth ,52,*  173,  210.* 
Shasta,  height  of,  307. 
Sigillaria  Hallii,  106. 

Carboniferous,  125.* 
Silica,  or  Quartz,  14. 
Silicates,  15. 

Siliceous    shells,  microscopic, 
59,*  61,*  108,*  267. 

waters  of  Geysers,  316. 
Silt,  282. 
Silurian  age,  79. 

Upper,  93. 

Siphonia  lobata,  189.* 
Slate,  22,  24. 
Slaty  cleavage,  36,*  329. 
Sloths,   gigantic,    of   Quater- 
nary, 236.* 
Snakes,  first  of,  210. 
Soapstone,  18. 

Solenhofen  lithographic  lime- 
stone, 161. 
Solfataras,  315 
Solitaire,  242.* 
South  America,  form  of,  9. 

changes  of  level  in,  231 
Species,  exterminations  of.  92, 

147, 198,  200,  252,  255. 
Sphagnous  mosses,  265. 
Sphenopteris      Gravenhorstii, 

125.* 
Spicules  of  Sponges,  59, 108,* 

Spiders,  53, 130.* 
Spinax  Blainvillii,  52.* 
Spirifer  cameratus,  129.* 

macropleurus,  98  * 

mucronatus.  110  * 

Walcotti,  169.* 
Spirifers,  last  of,  174,*  200. 
Sponges,  59,*  188.* 

Cretaceous,  188,*  189.* 
Sponge-spicules,  59,  189. 

in  hornstone,  108.* 
Spores  in  coal,  134.* 
Stalactites,  26. 
Stalagmite,  26. 
Star-fishes,  58.* 
Statuary  marble,  26. 
Steatite,  18. 
Stigmarise,  126.* 
Strata,  definition  of,  27. 

positions  of,  37,*  39  *  44. 
Stratification,  27,*  31.* 
Strike,  41.* 
Strophomena      rhomboidalis, 

96.* 
Subcarboniferons  period,  113, 

119. 

Submarine  eruptions,  314. 
Subsidence  of  coast  of  New 
Jersey,  232. 

of  Greenland,  recent,  232 
Subsidences    of  volcanic    re- 
gions, 314. 

Subterranean  waters,  284. 
Sweden,  Quaternary  of,  229. 

changes  of  level  in,  232. 
Syenyte,  24,  26. 


358 


INDEX. 


Synclinal,  42.* 
Synclinorium,  335. 
Syringopora  Maclurii,  109.* 
Talc,  18. 

Talcose  schist,  23. 
Tapirus  Indicus,  211. 
Teliost  fishes  50.* 

Cretaceous,  191,*  200. 

Tertiary,  209. 
Tentaculites,  97.* 
Terraces  on  Connecticut  River, 
227.* 

of  Scotland,  229. 

origin  of,  225,  229. 
Tertiary  age,  206. 
Tetradecapods,  53.* 
Tetragonolepis,  173.* 
Thallogens,  60 
Thanet  sands,  206. 
Thecodonts,  133. 
Thrissops,  51.* 
Tidal  currents,  288. 
Tiger,  215 

Time,  length  of  geological, 245. 
Time-ratios,  140,  196,  245. 
Titanothere,  214.* 
Tourmaline,  17.* 
Trachyte,  27. 
Tracks  of  birds,  167.* 

Cheirotherium,  174.* 

of  insects,  166.* 

of  reptiles,  Carboniferous, 
132.* 

of  reptiles,  Triassic,  166. 


Tracks  of  trilobites,  28.* 
Transportation  by  rivers,  281. 
Trap, 26. 

of  Connecticut  Valley ,  etc. , 
160. 

columnar,  319.* 
Travertine,  26. 
Tree-ferns,  125  * 
Trenton  period,  84.    • 
Triassic  period,  159. 
Trigonia  clavellata,  169  * 
Trigonocarpus    tricuspidatus, 

125.* 

Trilobites,  54  *  81,*  88  *  96* 
150. 

beginning  and  ending  of 

genera,  147. 
Tufa,  23,  308 

Turrilites  catenatus,  191.* 
Turritella  carinata,  208  * 
Turtles,  Cretaceous,  193. 

Jurassic,  177. 

Tertiary,  210. 

Unconformable  strata,  43.* 
Under-clays,  120. 
Unstratified  condition,  29.* 
Upper  Helderberg,  103. 
Upper  Silurian,  93. 
Ursus  spelseus,  233. 
Utica  shale,  86. 

Valleys,  formation  of,  277. 
Veins,  29.* 


Veins,  formation  of.  323. 
Vertebrate-tailed    fishes,   51  * 

112-* 
Vertebrates,  49,  50. 

first  of,  98. 
Vesuvius,  303 
Viviparus  fluviorum,  169.* 
Volcanoes,  306. 

Water,  action  of,  275. 

subterranean,  284. 

freezing  and  frozen,  294. 
Water  lime  group,  94. 
Waves,  action  of,  287. 
Wealden,  161. 
Wenlock  limestone,  95. 
Whales,  first  of,  210. 
Winds,  effects  of,  273 
Wind-drift  structure, 32* 274. 
Woolwich  beds,  206. 
Worms,  53,*  82. 

Xiphodon  gracile,  212. 

Yoldia  limatula,  209.* 
Yorktown  period,  203. 

Zamia,  62, 162. 
Zaphrentis  bilateralis,  96.* 

Rafinesquii,  109.* 
Zeacrinus  elegans,  129.* 
Zeuglodon,  212. 


THE   END. 


University  Press,  Cambridge:  Electrotyped  and  Printed  by  Welch,  Bigelow,  &  Co. 


VB  24056 


